Quinine, an old anti-malarial drug in a modern world: role in the treatment of malaria.
Journal: 2011/September - Malaria Journal
ISSN: 1475-2875
Abstract:
Quinine remains an important anti-malarial drug almost 400 years after its effectiveness was first documented. However, its continued use is challenged by its poor tolerability, poor compliance with complex dosing regimens, and the availability of more efficacious anti-malarial drugs. This article reviews the historical role of quinine, considers its current usage and provides insight into its appropriate future use in the treatment of malaria. In light of recent research findings intravenous artesunate should be the first-line drug for severe malaria, with quinine as an alternative. The role of rectal quinine as pre-referral treatment for severe malaria has not been fully explored, but it remains a promising intervention. In pregnancy, quinine continues to play a critical role in the management of malaria, especially in the first trimester, and it will remain a mainstay of treatment until safer alternatives become available. For uncomplicated malaria, artemisinin-based combination therapy (ACT) offers a better option than quinine though the difficulty of maintaining a steady supply of ACT in resource-limited settings renders the rapid withdrawal of quinine for uncomplicated malaria cases risky. The best approach would be to identify solutions to ACT stock-outs, maintain quinine in case of ACT stock-outs, and evaluate strategies for improving quinine treatment outcomes by combining it with antibiotics. In HIV and TB infected populations, concerns about potential interactions between quinine and antiretroviral and anti-tuberculosis drugs exist, and these will need further research and pharmacovigilance.
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Malaria Journal. Dec/31/2010; 10: 144-144
Published online May/23/2011

Quinine, an old anti-malarial drug in a modern world: role in the treatment of malaria

Abstract

Background and historical perspective

The discovery of quinine is considered the most serendipitous medical discovery of the 17th century [1] and malaria treatment with quinine marked the first successful use of a chemical compound to treat an infectious disease[2]. Quinine, as a component of the bark of the cinchona (quina-quina) tree, was used to treat malaria from as early as the 1600s, when it was referred to as the "Jesuits' bark," "cardinal's bark," or "sacred bark." These names stem from its use in 1630 by Jesuit missionaries in South America, though a legend suggests earlier use by the native population[2]. According to this legend, an Indian with a high fever was lost in an Andean jungle. Thirsty, he drank from a pool of stagnant water and found that it tasted bitter. Realizing that the water had been contaminated by the surrounding quina-quina trees he thought he was poisoned. Surprisingly, his fever soon abated, and he shared this accidental discovery with fellow villagers, who thereafter used extracts from the quina-quina bark to treat fever [3]. The legend of quinine's discovery accepted in Europe differs though, and involves the Spanish Countess of Chinchon who, while in Peru, contracted a fever that was cured by the bark of a tree. Returning to Spain with the bark, she introduced quinine to Europe in 1638 and, in 1742, botanist Carl Linnaeus called the tree "Cinchona" in her honour [4].

Before 1820, the bark of the cinchona tree was first dried, ground to a fine powder, and then mixed into a liquid (commonly wine) before being drunk. In 1820, quinine was extracted from the bark, isolated and named by Pierre Joseph Pelletier and Joseph Caventou. Purified quinine then replaced the bark as the standard treatment for malaria [5]. Quinine and other cinchona alkaloids including quinidine, cinchonine and cinchonidine are all effective against malaria. The efficacies of these four alkaloids were evaluated in one of the earliest clinical trials, conducted from 1866 to 1868 in 3600 patients using prepared sulfates of the alkaloids. With the main outcome measure of "cessation of febrile paroxysms", all four alkaloids were found to be comparable, with cure rates of >98%[6]. However, after 1890 quinine became the predominantly used alkaloid, mainly due to a change in supply from South American to Javan cinchona bark, which contained a higher proportion of quinine [7]. Quinine remained the mainstay of malaria treatment until the 1920s, when more effective synthetic anti-malarials became available. The most important of these drugs was chloroquine, which was extensively used, especially beginning in the 1940s [6]. With heavy use, chloroquine resistance developed slowly. Resistance of Plasmodium falciparum to chloroquine was seen in parts of Southeast Asia and South America by the late 1950s, and was widespread in almost all areas with falciparum malaria by the 1980s. With increasing resistance to chloroquine, quinine again played a key role, particularly in the treatment of severe malaria [6]. To-date quinine continues to play a significant role in the management of malaria. This review, discusses the historical role of quinine, considers its current usage, and provides insight into the appropriate future use of quinine for the treatment of malaria. Information was obtained by searching published literature in the National Library of Medicine via Pub Med and MEDLINE search engines for research articles, reviews, books, and other reports. Identification of published reports was done using key word searches such as quinine and malaria treatment, quinine and drug resistance, quinine in pregnancy, quinine and antibiotic combinations, and quinine and HIV/TB infected populations.

Quinine properties

Quinine is a cinchona alkaloid that belongs to the aryl amino alcohol group of drugs. It is an extremely basic compound and is, therefore, always presented as a salt[6]. Various preparations exist, including the hydrochloride, dihydrochloride, sulphate, bisulphate, and gluconate salts; of these the dihydrochloride is the most widely used. Quinine has rapid schizonticidal action against intra-erythrocytic malaria parasites. It is also gametocytocidal for Plasmodium vivax and Plasmodium malariae, but not for Plasmodium falciparum. Quinine also has analgesic, but not antipyretic properties. The anti-malarial mechanism of action of quinine is unknown.

Quinine is rapidly absorbed both orally and parenterally, reaching peak concentrations within 1-3 hours[8]. It is distributed throughout the body fluids and is highly protein bound, mainly to alpha-1 acid glycoprotein. The binding capacity in plasma is concentration dependent, but also depends on the levels of alpha-1 acid glycoprotein, which therefore makes comparisons between different studies difficult[9]. Quinine readily crosses the placental barrier and is also found in cerebral spinal fluid. Excretion is rapid - 80% of the administered drug is eliminated by hepatic biotransformation and the remaining 20% is excreted unchanged by the kidney [10-12]. The half-life of quinine ranges between 11-18 hours [13,14]. Several pharmacokinetic characteristics of quinine differ according to the age of the subject and are also affected by malaria. The volume of distribution is less in young children than in adults, and the rate of elimination is slower in the elderly than in young adults. In patients with acute malaria the volume of distribution is reduced and systemic clearance is slower than in healthy subjects; these changes are proportional to the severity of the disease. As a result, plasma quinine levels are higher in patients with malaria. Protein binding of quinine is increased in patients with malaria as a result of an increased circulating concentration of alpha-1 acid glycoprotein [15].

Quinine has a low therapeutic index, and adverse effects with its use are substantial [16]. The side effects commonly seen at therapeutic concentrations are referred to as cinchonism, with mild forms including tinnitus, slight impairment of hearing, headache and nausea. Impairment of hearing is usually concentration dependent and reversible [17]. More severe manifestations include vertigo, vomiting, abdominal pain, diarrhea, marked auditory loss, and visual symptoms, including loss of vision. Hypotension may occur if the drug is given too rapidly, and venous thrombosis may occur following intravenous injections [10]. Intramuscular administration is painful and may cause sterile abscesses. Hypoglycaemia is yet another common side effect of quinine therapy [15,18] and is a particular problem in pregnant women[19]. Hypoglycaemia has been reported to occur in up to 32% of patients receiving quinine therapy[18]. However in more recent studies, hypoglycaemia occurred in only 3% of adults and 2.8% of African children receiving quinine [20,21]. Less frequent but more serious side effects of quinine therapy include skin eruptions, asthma, thrombocytopaenia, hepatic injury and psychosis [22].

Overview of quinine use in the management of malaria

Quinine remains an important anti-malarial drug, almost 400 years after Jesuit priests first documented its effectiveness. The 2010 World Health Organisation (WHO) guidelines recommend a combination of quinine plus doxycycline, tetracycline or clindamycin as second-line treatment for uncomplicated malaria (to be used when the first-line drug fails or is not available) and quinine plus clindamycin for treatment of malaria in the first trimester of pregnancy [23]. Based on recent trials, intravenous artesunate should be used for the treatment of severe falciparum malaria in adults [20] and children[21], in preference to quinine.

By 2009, 31 African countries recommended quinine as second-line treatment for uncomplicated malaria, 38 as first-line treatment of severe malaria and 32 for treatment of malaria in the first trimester of pregnancy [24]. In most of Africa, quinine is still used as monotherapy, contrary to the WHO recommendations[23,24]; the reason for this practice may be the higher costs of quinine-antibiotic combinations. Quinine continues to play a significant role in the management of malaria in sub-Saharan Africa and other malaria endemic areas, and its use in routine practice may not be restricted to the stated WHO recommendations. In Cameroon, even one year after the introduction of ACT, quinine continued to be used as first-line therapy, with 45% of adults receiving oral quinine for uncomplicated malaria [25]. Recent surveillance data from sentinel sites in Uganda showed that quinine was prescribed for up to 90% of children < 5 years with uncomplicated malaria [26].

The use of quinine for uncomplicated malaria cases should have decreased due to toxicities, poor compliance and the implementation of newer and better tolerated therapies such as ACT. However, the limited availability of ACT and the increasing resistance to chloroquine and antifolates have actually increased its use in recent times [27]. Therefore, studies evaluating the role of quinine in the management of malaria have been reviewed.

Quinine for uncomplicated malaria

In several settings, oral quinine continues to be used as treatment for uncomplicated malaria, a practice mainly resulting from frequent stock-outs of the recommended ACT [26,28]. Previous studies of the effectiveness and efficacy of quinine for uncomplicated malaria showed mixed results (Table 1). The majority of these studies were conducted in settings with reported declining efficacy of quinine in Southeast Asia and South America. Earlier studies in these regions, using varying dosing regimens, showed cure rates ranging from 76% to 98%. The lower cure rates were mainly observed with shorter regimens (3 days) and higher cure rates when the drug was combined with sulphadoxine-pyrimethamine, tetracycline or clindamycin [29-34]. Similar findings were reported in Vietnam, where a three-day course of quinine plus artesunate had a cure rate of only 50%, compared to a five-day course, which had a cure rate of 76%[35]. Studies in Southeast Asia using quinine monotherapy for 7 days showed cure rates of 85-87% [29,33], which is similar to what was observed over 15 years earlier [36], (Table 1).

Table 1
Summary of studies of quinine for the treatment of uncomplicated malaria
Study siteYearSample size and study populationDrug RegimensDuration of follow-upTreatment outcomeCommentReference
Thailand, region with multidrug resistant malaria1984-198566 children
2-12 years
Quinine Quinidine28 days
DOT
Cure rates:
Quinine - 85%
Quinidine - 88%
Treatment failures only RI responses[29]

Cambodia, region with multidrug resistant malaria1983119 adults,
>15 years
Mefloquine +SP (MSP)
3 days quinine+tetracycline (Q3T7)
7 days of quinine+ tetracycline (Q7T7)
28 days
DOT
Cure rates:
MSP: 98%
Q3T7: 76%
Q7T7: 92%
Q7T7 still gives good cure rate[30]

Brazil, setting with quinine resistance1985100 patients
18-55 years
Mefloquine 1000 mg single dose (MQ)
3 days quinine+SP (Q3+SP)
42 days
DOT
Cure rates:
MQ:
96%
Q3 + SP: 98%
Four RI responses in Q3 + SP group[31]

Thailand, region with multidrug resistant malaria1994102 patients
16-60 years
Mefloquine+tetracycline (MQT)
7 days of Quinine+ tetracycline (Q7T7)
28 days
DOT
Cure rates:
MQT: 94%
Q7T7: 98%
MQ + Tetra as effective as Q7T7[34]

Thailand, region with multidrug resistant malaria1995-1997204 male patients
15-64 years
7 days quinine (Q7)
Quinine + tetracycline (Q7T7)
Quinine + clindamycin (Q7C7)
28 days
Directly observed therapy
Cure rates:
Q7: 87%
Q7T7: 98%
Q7C7: 100%
Tetracycline or clindamycin improves quinine cure rates[33]

Equatorial Guinea, setting with no quinine resistance1999114 children
6-59 months
7days quinine (Q7)
Chloroquine (CQ)
Sulfadoxine/pyrimethamine (SP)
114 day follow-upCure rates:
Q7: 94.5%
CQ: 60%
SP: 90%
Quinine is effective against P.falciparum malaria[43]

Cameroon, High transmission setting200530 children
0.5-6 years
5 days quinine (Q5)14 day follow-upCure rates: 100%[41]

Burundi Perennial transmission setting1992-1995472 children
0-14 years
Chloroquine (CQ)
5 days quinine (Q5)
7 day follow-upFailure rates Q5:
1992-1993: 4.2%
1994-1995: 7.1%
[40]

Guinea-Bissau Perennial transmission setting1994-1995203 children
0.7-13 years
3 days quinine (Q3)
5 days quinine (Q5)
7 days quinine (Q7)
28-35 day follow-upDay 28 recurrent parasitemia:
Q3: 79%
Q5: 90%
Q7: 11%
3 day quinine regimens should not be used.[37]

Gabon High transmission setting1993-1994120 adults = 15years3 days quinine (Q3)
3 days quinine+clindamycin (Q3C3)
3 days quinine+doxycycline (Q3D3)
28 day follow-upDay 28 cure rates:
Q3: 38%
Q3C3: 92%
Q3D3: 91%
The two short course combinations of quinine had excellent cure rates[109]

Uganda Meso-endemic transmission setting2007-2008175 children
6months - 5 years
7 days quinine (Q7)
3 days artemether-lumefantrine (AL)
28 day follow-upCure rates:
Q7: 64%
AL: 97%
Results question the advisability of quinine use for uncomplicated malaria[45]

Moreover, the addition of either tetracycline or clindamycin to quinine in the Thai study improved cure rates to 98% and 100% respectively and also delayed the appearance of Plasmodium vivax infection, suggesting additional activity against this species [33].

In Africa, studies evaluating three-day quinine treatment regimens have usually found unacceptably high failure rates [37], with recurrent infections at day 28 post-treatment experienced in 30% - 50% of patients[37-39]. However most of these studies did not perform PCR analyses to distinguish between recrudescence and re-infection, leading to possible underestimation of efficacy. In interpreting these results, the malaria transmission intensity at the study sites needs to be taken into consideration, as high treatment failure rates in high transmission settings may be due to a high risk of new infections. Additional PCR unadjusted studies that have evaluated five-day regimens of quinine have found recurrent infection rates on day 7 between 4% and 7% [40] and day 14 treatment failure rates of 0 to 5% (Table 1) [41,42]. In Equatorial Guinea, five-day courses of quinine were associated with day 14 PCR unadjusted failure rates as high as 22%. These latter results prompted a change in the quinine treatment regimen for this region to a 7 day course, with subsequent significant decrease in treatment failure rates to 3%-5.5% [43]. This study also reported that treatment failure rates with quinine remained stable over the five-year period of surveillance.

Even with seven-day treatment durations, evaluations of different quinine dosage regimens have revealed interesting trends. Doses of 10 mg/kg/day given twice daily for 7 days were associated with day 28 treatment failure rates as high as 30%[37]. Increasing the quinine dosage to 15 mg/kg/day or 20 mg/kg/day improved treatment outcomes, with failure rates ranging from 8% to 14%[37], although potential increases in toxicity with higher dosages are a concern. The treatment regimen currently recommended in sub-Saharan Africa is 10 mg/kg of the base given 8 hourly for 7 days. This regimen was associated with a lower rate of recurrent infections on day 28 (6.3%) compared to the 10 mg/kg twice daily regimen (16.1%)[44].

The advent of ACT has provided important new therapeutic options for the management of uncomplicated malaria in regions with high prevalence of multi-drug resistant malaria. A few available trials have shown superiority of ACT over quinine in the management of uncomplicated malaria [32,45,46]. In Brazil, patients treated with artemether-lumefantrine (AL) had significantly faster parasite clearance times when compared to those treated with quinine+doxycycline [46]. Considering the extensive available data, quinine should not be used to treat uncomplicated malaria when ACT is available [27,45]. ACT has the advantages of simplicity of dosing, which promotes adherence to therapy when compared with the seven-day treatment courses of quinine [32,45], better tolerance and decreased risks of serious toxicity.

Nevertheless, despite their scale up in Africa, the cost and availability of ACT in the public sector remains a major challenge. In 2008, ACT coverage in the public sector in high-burden African countries was only 42%[47]. Similarly, a survey carried out during the same year in seven African countries showed that the percentage of fever cases in children < 5 years treated with ACT was only 16% [47]. The sustainability of ACT supplies in resource limited settings therefore presents a huge problem, with stock-outs consistently occurring in health facilities [48]. Quinine, on the other hand, is a relatively cheap drug and often the only available option, rendering its rapid withdrawal for uncomplicated malaria cases risky. The best approach in these settings would be to proactively identify solutions to ACT stock-outs and maintain quinine as a fall-back drug only in case of ACT stock-outs. Additionally, improving quinine treatment outcomes by combining it with antibiotics, such as tetracycline or clindamycin [49-51], could be investigated and promoted. More recently, combinations of quinine and newer antibiotics with shorter treatment regimens that would improve adherence to therapy as well as minimize related adverse events have been evaluated. One such combination is that with azithromycin which is of particular interest, as the drugs act synergistically [52]. This combination offers promise for use especially in pregnant women and children < 8 years, since, unlike tetracyclines, both drugs are safe in these groups. A study in Thailand showed comparable efficacy in the treatment of multidrug resistant malaria, with cure rates of 100%, for a seven-day course of quinine+doxycycline and a three-day course of quinine+azithromycin [49]. These drug combinations will need further evaluation to confirm these findings and may offer a solution to the compliance problems associated with seven-day courses of quinine.

Quinine for malaria in pregnancy

Malaria in pregnancy causes several adverse outcomes that include maternal anaemia, intrauterine growth retardation, low birth weight, preterm deliveries and abortion. Prevention and treatment of malaria in pregnancy is, therefore, critical to avoid these adverse outcomes. Currently the WHO recommends the use of quinine plus clindamycin for treating malaria in the first trimester of pregnancy, as the safety of artemisinin compounds during this period is not yet established [23]. As most clinical trials exclude women in their first trimester of pregnancy, information on the efficacy and safety of anti-malarial drugs during this period is extremely limited. Evidence for the safety of quinine in pregnancy is mostly historical and there are few clinical trials published [50,53]. Clindamycin on the other hand has a good safety record in pregnancy [54] and its pharmacokinetic properties are usually unchanged by pregnancy[55]. The combination of quinine and clindamycin has proven highly efficacious against multidrug-resistant strains of P. falciparum, with 42 day cure rates of 100% in one study [50]. The only concern with this combination is that it is usually not affordable for most resource limited settings. For the second and third trimester of pregnancy, quinine monotherapy seems to have unacceptably low efficacy in areas with multidrug resistant malaria when compared to ACT. Studies in these regions have shown that ACT performs better than oral quinine in terms of parasite clearance and fever clearance. Two studies in Thailand [56,57] reported fewer treatment failures at day 63 with artesunate plus atovaquone-proguanil and artesunate plus mefloquine, when compared with quinine. The occurrence of adverse events experienced by the pregnant women was similar in all groups, although tinnitus was more frequent in the quinine group. In these studies, the considerably inferior efficacy of quinine was attributed to both drug resistance and to the varying pharmacokinetic properties of quinine during pregnancy. In Africa however, available evidence suggests that Plasmodium. falciparum generally remains sensitive to quinine [58] and low cure rates with quinine monotherapy in pregnant women has been mainly attributed to poor compliance to treatment [59]. Thus in Africa, quinine monotherapy remains the most widely used treatment for malaria in the first trimester of pregnancy and is also considered safe during all trimesters of pregnancy. A recent study from Uganda provides important reassurance of continued efficacy of quinine monotherapy in these regions of Africa. In this study, quinine and artemether-lumefantrine had similar efficacy for the treatment of uncomplicated malaria in the second and third trimesters of pregnancy [60]. The evidence for safety of ACT use during the first trimester of pregnancy is currently limited [61]. Therefore, until more data become available, the recommendation to use quinine in the first trimester of pregnancy will remain and ACT should only be used in the second and third trimesters of pregnancy. Patient education and counseling will however be critical to promote compliance with therapy.

Quinine in HIV or tuberculosis infected populations

Interactions between HIV and malaria remain a major public health concern in areas affected by both diseases. Very few studies have evaluated the role of quinine in the management of malaria in HIV infected populations. The earliest study was done in the Congo in 1986 and it showed malaria cure rates of 92% in HIV infected patients treated with oral quinine with comparable results in HIV-negative patients [62]. In a subsequent study in the same region, no significant differences in treatment response were observed between children with progressive HIV infection and HIV-uninfected controls treated with oral quinine [63]. Such findings and other available data suggest that malaria treatment policy in HIV infected populations can generally follow the standard practices. Concerns however remain about potential interactions between anti-malarial and anti-retroviral drugs. Currently, there is little published information on the co-administration of antiretroviral therapy (ART) and anti-malarial drugs, yet this will become increasingly important with the rapid scale-up of ART in Africa. In Nigeria, concurrent administration of nevirapine and quinine led to significant reductions in the plasma levels of quinine and elevated plasma levels of 3-hydroxyquinine, the major metabolite of quinine [64]. This could potentially reduce the efficacy of quinine while increasing toxicity, since 3-hydroxyquinine has higher toxicity and lower anti-malarial activity than quinine. Interactions with ritonavir have also been described, with concurrent administration of these drugs leading to marked elevations in plasma levels of quinine and decreases in levels of 3-hydroxyquinine [65]. These results suggest the need for downward dosage adjustments of quinine with concurrent administration of ritonavir, including ritonavir-boosted protease inhibitor regimens.

The co-existence of tuberculosis (TB), malaria and HIV in sub-Saharan Africa and other settings causes additional concerns about their treatment. Interactions between rifampicin (a major component of first-line anti-TB treatment regimens) and quinine would be expected as rifampicin is a potent inducer of hepatic enzymes and quinine is metabolised mainly by the human CYP 3A isoenzyme. In vivo studies in healthy volunteers showed that when quinine was administered with rifampicin its mean clearance was significantly greater and mean elimination half-life shorter [66]. Interesting observations of the effect of combined quinine and rifampicin therapy were additionally reported in Thai patients with uncomplicated malaria [67]. In this study, parasite clearance times were shorter in the quinine-rifampicin group than in the group given quinine monotherapy, suggesting that the anti-malarial activity of rifampicin augmented that of quinine initially. However, recrudescence rates were five times higher in the quinine-rifampicin group than in the quinine-alone group[67]. These observations were explained by marked differences in the plasma quinine concentrations when rifampicin was combined with quinine. These results suggest that the quinine dosage might need to be increased in patients receiving rifampicin as an anti-TB drug.

Concerns also exist about potential interactions with the concurrent use of antiretroviral drugs and artemisinin-based combination therapy [68-70]. Further research and pharmacovigilance will be critical to facilitate the development of targeted treatment recommendations. Presently, it is not possible to elucidate advantages associated with the use of any particular anti-malarial drug for HIV or TB infected populations.

Quinine in the management of severe malaria

The treatment of severe malaria requires prompt, safe, and effective intravenous anti-malarial drugs. Over the years, quinine has been the mainstay in the treatment of severe malaria and still remains the first line drug in most African countries [24]. Though quinine dosing regimens have varied, the WHO recommends a dose of 20 mg salt/kg by intravenous infusion, then 10 mg/kg every eight hours [23]. The rationale for the loading dose is the urgent need to achieve therapeutic plasma concentrations. One systematic review showed that a loading dose of quinine reduced fever and parasite clearance times, but there was insufficient data to demonstrate its impact on risk of death [71].

More recently, intravenous artesunate is the recommended treatment of choice for severe falciparum malaria in adults [23]. This recommendation was made on the basis of the dramatic results of the SEAQUAMAT trial conducted in Southeast Asia that showed a 35% reduction in the case-fatality rate in adults with severe malaria treated with intravenous artesunate compared to intravenous quinine[20]. Subsequent systematic reviews have also provided additional evidence for this recommendation [72]. However, about 80% of malaria deaths occur in sub-Saharan Africa among children aged < 5 years. The therapeutic options previously recommended by WHO for the paediatric group included intravenous artesunate, intramuscular artemether or intravenous quinine[23]. Several trials and meta-analyses comparing intramuscular artemether with intravenous quinine have consistently shown no benefit of treatment with artemether over quinine in children with severe malaria in sub-Saharan Africa [73-75] (Table 2). The recently concluded AQUAMAT study now provides conclusive evidence of the superiority of intravenous artesunate over quinine in children <15 years, with a relative reduction of 23% in mortality associated with the use of artesunate[21]. These observations recently led to a change in WHO recommendations, with intravenous artesunate now advocated in preference to quinine for the management of severe malaria in children. The most critical issues that will need to be addressed, however, are the availability of intravenous artesunate for the patients who need it, especially in resource-limited settings, and its effectiveness in real-life settings. Until recently, the available formulations of injectable artesunate that have been used in several clinical trials were not produced according to Good Manufacturing Practices (GMP) and this could be a problem for African countries relying on donors who do not permit purchase of non-GMP artesunate. WHO recently pre-qualified intravenous artesunate manufactured by Guilin Pharmaceuticals in China and this may resolve problems of procurement of GMP artesunate. However, it is unclear whether supplies will be sufficient for the thousands of patients in need. Until these procurement and supplies issues are resolved, intravenous quinine may remain the only readily available drug for treating severe malaria in sub-Saharan Africa and other resource-limited settings. Furthermore, there are several health systems challenges related to the management of severe malaria in resource limited settings that impact on treatment outcomes, independent of the parenteral anti-malarial drugs used. Consequently, changes in treatment policies, in this case from quinine to artesunate, may not offer improvements without considering drug availability as well as additional measures to strengthen health systems.

Table 2
Summary of studies of quinine for the treatment of severe malaria
Study siteYearSample size and Study populationDrug RegimensTreatment outcomeCommentReference
Gambia1992-1994576 children
1-9 years Cerebral malaria
Intramuscular artemether (IMA)
Intravenous quinine (IVQ)
Mortality:
IMA:20.5%
IVQ: 21.5%
Neurological sequelae:
IMA: 3.3%
IVQ: 5.3%
Artemether is as effective as quinine in treatment of cerebral malaria in children[74]

Malawi1992-1994183 children
Cerebral malaria
Intramuscular artemether (IMA)
Intravenous quinine (IVQ)
Mortality:
IMA: 11%
IVQ: 16%
Survival with neurological sequelae:
IMA: 19%
IVQ: 12%
Results do not suggest artemether would confer a survival advantage over quinine[73]

Kenya2000-2002360 patients
1-60 years
Severe malaria
IV Quinine + oral malarone (QM)
IV Quinine +oral quinine (QQ)
Day 28 cure rates:
QM: 98.7%
QQ: 90%
Using malarone after IV quinine is safer and as effective as IV quinine +oral quinine[87]

Burkina Faso2001-2002898 children
1-15 years
Moderately severe malaria
Rectal quinine (RQ)
Intramuscular quinine (IMQ)
Early treatment failure (day 3):
RQ: 6%
IMQ: 3%
Fever recurrence on day 7:
RQ: 5%
IMQ: 10%
Rectal quinine had acceptable safety profile and could be used as early treatment for severe malaria[84]

Uganda2002-2003103 children
0.5-5 years
Cerebral malaria
Rectal artemether (RA)
Intravenous quinine (IVQ)
Mortality:
IVQ: 11.7%
RA: 19.2%
Rectal artemether was effective and well tolerated[76]

S.E Asia (Four countries)2003-20051461 patients
>2 years
Severe malaria
Intravenous artesunate (IVA)
Intravenous quinine (IVQ)
Mortality:
IVA: 15%
IVQ: 22%
Absolute reduction in mortality: 34.7%
Intravenous artesunate should be treatment of choice for severe malaria in adults[20]

Uganda2003-2004110 children
0.5-5 years
Cerebral malaria
Rectal quinine (RQ)
Intravenous quinine (IVQ)
Mortality:
RQ: 7%
IVQ: 9%
Comparable clinical and parasitological outcomes
Rectal quinine was efficacious and could be used as a treatment alternative[79]

Africa (Nine countries)2005-20105425 children
< 15 years Severe malaria
Intravenous artesunate (IVA)
Intravenous quinine (IVQ)
Mortality:
IVA: 8.5%
IVQ: 10.9%
Relative reduction in mortality: 22.5%
Parenteral artesunate should replace quinine as the treatment of choice for severe malaria[21]

Another important aspect of severe malaria case management is pre-referral treatment, which is treatment given to a patient with severe malaria before they are referred to a health facility. This is critical, as most malaria deaths, especially in Africa, occur outside hospitals, either in the communities or at lower levels of care. Studies evaluating the role of rectal artesunate and artemether as pre-referral treatment have found these options to be highly efficacious [76,77]. However, the biggest challenge faced in resource limited settings has been the non-availability of these preparations in health facilities. A recent survey in Uganda found that rectal artemisinins were available in only 5% of the health facilities despite the fact that this is the recommended pre-referral drug [78]. A feasible alternative is rectal quinine, which has been found to have comparable efficacy with intravenous quinine in the management of severe malaria in children [79-84] (Table 2) and could play a more significant role than currently acknowledged as pre-referral treatment for severe malaria. More recent studies in Senegal and Mali provide additional support for the efficacy and feasibility of this route and also show that a pre-referral kit of rectal quinine was acceptable to both caretakers and health workers [85,86].

Following successful administration of parenteral treatment for severe malaria, it is recommended to continue with an oral anti-malarial drug once a patient is able to tolerate oral therapy. The current practice is to continue the same medicine orally as given parenterally to complete a full treatment course [23]. The options for oral continuation therapy that are available in many African settings would therefore include oral quinine or an ACT. In non-pregnant adults, doxycyline would also be added to either of these drugs and given twice daily for 7 days. Where available, clindamycin may be substituted in children, since doxycyline is contraindicated in this age group [23]. The choice of oral continuation therapy following initial parenteral treatment of severe malaria may also have an impact on clinical outcomes, particularly on parasite clearance, fever clearance and potentially the risk of recurrent parasitaemia. In this regard completing intravenous quinine treatment with an ACT instead of oral quinine may improve the overall treatment outcome of parenteral quinine therapy. Studies evaluating this approach to therapy are limited. A study in Kenya during 2000-2002, showed that completing the intravenous quinine dose with oral malarone (atovaquone + proguanil) was associated with improved clinical outcomes compared to intravenous quinine followed by oral quinine [87] (Table 2). Additional studies should explore other options, in particular ACT, for improving therapeutic outcomes with intravenous quinine treatment.

Potential explanations for quinine treatment failure

Quinine resistance

Parasite drug resistance is probably the greatest problem faced by malaria control programs worldwide and is an important public health concern. Over the years, malaria parasites have developed resistance to a number of commonly used anti-malarial drugs. However the development of resistance to quinine has been slow. Although its use started in the 17th century, resistance to quinine was first reported in 1910 [88]. In comparison, resistance to chloroquine and proguanil emerged within only 12 [89] and 1 year [88,90] of their introduction, respectively. Resistance to quinine is usually low grade, with the drug retaining some activity but having its action delayed or diminished. Diminished sensitivity of P. falciparum to quinine has been widely documented in Asia [91] and South America [92] but it seems relatively uncommon in Africa where conflicting results of no resistance [93,94] or varying degrees of resistance [95], [96] have been reported. A recent study from Thailand showed significant reductions in efficacy of quinine, artemisinin and mefloquine when compared to previous reports from the same area, suggesting further increase in drug resistance in this region [97]. No convincing evidence of high grade quinine resistance in the treatment of severe malaria has been reported. Findings from a recent systematic review of about 435 clinical trials published between 1966 and 2002 showed that the recrudescence rates for quinine reported over these past 30 years remained roughly constant [98]. These findings are encouraging and may suggest that efficacy of quinine has been preserved.

Variations in quinine pharmacokinetics

Treatment failures with quinine could also be explained by varying pharmacokinetic profiles of the drug. It is known that quinine pharmacokinetic properties and therapeutic responses vary with age, pregnancy, immunity and disease severity [99]. Also, as patients recover from malaria, there is usually an expansion of the volume of distribution and an increase in systemic clearance of quinine resulting in a decline in the average concentration of quinine in plasma [100]. These variations may lead to drug levels that may be inadequate to completely clear infection. The possibility that pharmacokinetic factors may explain quinine treatment failure was initially raised about 20 years ago when a Thai patient who had fatal severe malaria and apparent RIII resistance was found to have abnormally low levels of quinine despite adequate dosing [101]. Additional evidence for the impact of unusual quinine pharmacokinetics on treatment outcomes was provided by a more recent study describing early treatment failure in a patient with severe malaria with an abnormally high volume of distribution and increased quinine clearance, resulting in abnormally low quinine concentrations [102]. A few studies have proposed that an increase in the quinine dosage after the third day could compensate for declines in plasma drug levels during recovery, especially in areas with resistant P. falciparum [99]. However, this is not routinely practiced. Despite these anecdotal observations, there is little evidence for large variations in quinine pharmacokinetics [103] and the exact role that variations in drug levels play in quinine treatment responses is unclear.

Quinine drug quality and treatment compliance

The quality of quinine used in routine care could play a key role in clinical outcomes. Poor quality drugs remain a problem worldwide and are a serious public health threat. A study in Nigeria evaluating the quality of different anti-malarial drugs found that 37% of 225 anti-malarial drugs did not meet the tolerance limits set by United Sates Pharmacopeia (USP) for the amount of active ingredient, and 46% of these were formulations of quinine [104]. In Congo, Burundi and Angola only 89% of the declared active substance was found in quinine tablets, with high quantities of impurities reported [105]. Another worrying situation was unveiled in a survey in Cameroon, where nearly 74% of 70 quinine samples had no active ingredient [106]. Several other studies have also described varying problems with quinine drug quality in different settings [107,108]. Ideally, branded anti-malarial drugs should be used, but unfortunately, branded quinine products are not universally available in Africa and other malaria endemic settings. In addition, national drug regulators need to strengthen their roles in the monitoring of anti-malarial drug quality.

Another potential explanation for quinine treatment failures may be poor compliance. Quinine's prolonged treatment course and significant tolerability problems may lead to poor compliance, and hence poor therapeutic outcomes [32,45,59]. In this aspect, ACT has an advantage over quinine since it is administered once or twice daily over three days. A recent study in Uganda showed comparable compliance on day 3 of treatment in patients taking either quinine or artemether-lumefantrine. However, non-compliance to quinine greatly increased with increasing days on therapy to about 44% by day 7[45]. Promotion of shorter courses of quinine, especially in combination with antibiotics, should improve compliance as well as treatment outcomes [39,109].

Conclusion

In the near future, quinine will continue to play a significant role in the management of malaria, particularly in resource limited settings. Following the results of the SEAQUAMAT and AQUAMAT trials, artesunate is now recommended as the treatment of choice for severe malaria patients, with quinine only acting as an alternative when artesunate is not available. The role of rectal quinine as pre-referral treatment for severe malaria has not been fully explored, but this remains a promising intervention given the limited availability of rectal artemisinin preparations in resource limited settings. Quinine continues to play a critical role in the management of malaria in the first trimester of pregnancy, and will remain so until safer alternatives become available. The continued use of quinine in the management of uncomplicated malaria is a concern. Clearly, the seven day duration of therapy and thrice daily administration of quinine present a major challenge to completion of therapy, leading to sub-optimal treatment outcomes. In these situations, ACT is a better option given the simplicity of dosing and shorter treatment duration. However, because of the frequent ACT stock outs, the rapid withdrawal of quinine as a treatment option for uncomplicated malaria cases is risky. The best approach would be, besides improving the supply system, to maintain quinine as a fall-back drug in case of ACT stock-outs.

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

AJ, PJR and UD conceived the idea and wrote the first draft of the manuscript. All authors read and approved the final version

Acknowledgements and funding

We thank colleagues who have made useful comments on this manuscript. No funding was obtained for the preparation of this manuscript.

References

  • 1. How Was Quinine Discovered?http://www.ehow.com/facts_5828007_quinine-discovered_.html#ixzz1JrTqGgQq
  • 2. DavidBJacobyRMYEncyclopedia of Family Health2005Third
  • 3. Quininehttp://www.discoveriesinmedicine.com/Ni-Ra/Quinine.html
  • 4. Cinchona barkhttp://historyofmalaria.com/2010/02/cinchona-bark/
  • 5. DobsonSMaMPJ RThe history of antimalarial drugsAntimalarial Chemotherapy: Mechanisms of Action, Resistance, and New Directions in Drug Discovery2001Totowa, New Jersey: Humana Press1525[Google Scholar]
  • 6. Yakoub AdenAbdiOEGustafssonLars LEricssonOrjanUrbanHellgrenHandbook of Drugs for Tropical Parasitic Infections19952
  • 7. BFHSome notes on the Cinchona IndustryChemical News1931142129133[Google Scholar]
  • 8. SalakoLASowunmiADisposition of quinine in plasma, red blood cells and saliva after oral and intravenous administration to healthy adult AfricansEur J Clin Pharmacol1992422171174[PubMed][Google Scholar]
  • 9. MihalyGWChingMSKlejnMBPaullJSmallwoodRADifferences in the binding of quinine and quinidine to plasma proteinsBr J Clin Pharmacol1987246769774[PubMed][Google Scholar]
  • 10. WhiteNJThe treatment of malariaN Engl J Med199633511800806[PubMed][Google Scholar]
  • 11. Tracy. WLaJ. eAlfred Goodman Gilman LEL JGHChemotherapy of parasitic infectionsGoodman and Gilman's Pharmacological basis of therapeutics79978981[PubMed][Google Scholar]
  • 12. EsamaiFAyuoPOwino-OngorWRotichJNginduAObalaAOgaroFQuoqiaoLXingboGGuangqianLRectal dihydroartemisinin versus intravenous quinine in the treatment of severe malaria: a randomised clinical trialEast Afr Med J2000775273278[PubMed][Google Scholar]
  • 13. JamaludinAMohamedMNavaratnamVMohamedNYeohEWernsdorferWSingle-dose comparative kinetics and bioavailability study of quinine hydrochloride, quinidine sulfate and quinidine bisulfate sustained-release in healthy male volunteersActa Leiden19885713946[PubMed][Google Scholar]
  • 14. WhiteNJChanthavanichPKrishnaSBunchCSilamutKQuinine disposition kineticsBr J Clin Pharmacol1983164399403[PubMed][Google Scholar]
  • 15. WhiteNJAntimalarial pharmacokinetics and treatment regimensBr J Clin Pharmacol1992341110[PubMed][Google Scholar]
  • 16. WHOSevere and complicated malariaTrans R Soc Trop Med Hyg200094Suppl 1190[PubMed][Google Scholar]
  • 17. KarlssonKKHellgrenUAlvanGRomboLAudiometry as a possible indicator of quinine plasma concentration during treatment of malariaTrans R Soc Trop Med Hyg1990846765767[PubMed][Google Scholar]
  • 18. OkitolondaWDelacolletteCMalengreauMHenquinJCHigh incidence of hypoglycaemia in African patients treated with intravenous quinine for severe malariaBr Med J (Clin Res Ed)19872956600716718[PubMed][Google Scholar]
  • 19. LooareesuwanSPhillipsREWhiteNJKietinunSKarbwangJRackowCTurnerRCWarrellDAQuinine and severe falciparum malaria in late pregnancyLancet19852844548[PubMed][Google Scholar]
  • 20. DondorpANostenFStepniewskaKDayNWhiteNArtesunate versus quinine for treatment of severe falciparum malaria: a randomised trialLancet20053669487717725[PubMed][Google Scholar]
  • 21. DondorpAMFanelloCIHendriksenICGomesESeniAChhaganlalKDBojangKOlaosebikanRAnunobiNMaitlandKKivayaEAgbenyegaTNguahSBEvansJGesaseSKahabukaCMtoveGNadjmBDeenJMwanga-AmumpaireJNansumbaMKaremaCUmulisaNUwimanaAMokuoluOAAdedoyinOTJohnsonWBTshefuAKOnyambokoMASakulthaewTNgumWPSilamutKStepniewskaKWoodrowCJBethellDWillsBOnekoMPetoTEvon SeidleinLDayNPWhiteNJAQUAMAT groupArtesunate versus quinine in the treatment of severe falciparum malaria in African children (AQUAMAT): an open-label, randomised trialLancet376975316471657[Google Scholar]
  • 22. Antimalarial Martindale, The Extra Pharmacopoeia199330London: Pharmaceuitical Press
  • 23. WHOMalaria treatment guidelines2010
  • 24. WHOGlobal antimalarial drug policies database - WHO African region2009September edn
  • 25. SayangCGausseresMVernazza-LichtNMalvyDBleyDMilletPTreatment of malaria from monotherapy to artemisinin-based combination therapy by health professionals in rural health facilities in southern CameroonMalar J20098174[PubMed][Google Scholar]
  • 26. (UMSP) UMSPUMSP sentinel site malaria surveillance report July 20102010
  • 27. YekaAAchanJD'AlessandroUTalisunaAOQuinine monotherapy for treating uncomplicated malaria in the era of artemisinin-based combination therapy: an appropriate public health policy?Lancet Infect Dis200997448452[PubMed][Google Scholar]
  • 28. WasunnaBZurovacDGoodmanCASnowRWWhy don't health workers prescribe ACT? A qualitative study of factors affecting the prescription of artemether-lumefantrineMalar J2008729[PubMed][Google Scholar]
  • 29. SabchareonAChongsuphajaisiddhiTSinhasivanonVChanthavanichPAttanathPIn vivo and in vitro responses to quinine and quinidine of Plasmodium falciparumBull World Health Organ1988663347352[PubMed][Google Scholar]
  • 30. MeekSRDoberstynEBGauzereBAThanapanichCNordlanderEPhuphaisanSTreatment of falciparum malaria with quinne and tetracycline or combined mefloquine/sulfadoxine/pyrimethamine on the Thai-Kampuchean borderAm J Trop Med Hyg1986352246250[PubMed][Google Scholar]
  • 31. de SouzaJMShethUKde OliveiraRMRouletHde SouzaSDAn open, randomized, phase III clinical trial of mefloquine and of quinine plus sulfadoxine-pyrimethamine in the treatment of symptomatic falciparum malaria in BrazilBull World Health Organ1985633603609[PubMed][Google Scholar]
  • 32. FungladdaWHonradoERThimasarnKKitayapornDKarbwangJKamolratanakulPMasngammuengRCompliance with artesunate and quinine + tetracycline treatment of uncomplicated falciparum malaria in ThailandBull World Health Organ199876Suppl 15966[PubMed][Google Scholar]
  • 33. PukrittayakameeSChantraAVanijanontaSClemensRLooareesuwanSWhiteNJTherapeutic responses to quinine and clindamycin in multidrug-resistant falciparum malariaAntimicrob Agents Chemother200044923952398[PubMed][Google Scholar]
  • 34. LooareesuwanSVanijanontaSViravanCWilairatanaPCharoenlarpPLasserreRCanfieldCKyleDEWebsterHKRandomised trial of mefloquine-tetracycline and quinine-tetracycline for acute uncomplicated falciparum malariaActa Trop19945714753[PubMed][Google Scholar]
  • 35. de VriesPJBNVan ThienHHungLNAnhTKKagerPAHeisterkampSHCombinations of artemisinin and quinine for uncomplicated falciparum malaria: efficacy and pharmacodynamicsAntimicrob Agents Chemother200044513021308[PubMed][Google Scholar]
  • 36. HarinasutaTBDDrug resistant malaria with special reference to chemotherapyMosquito-Borne Diseases Bulletin1984123-30[Google Scholar]
  • 37. KofoedPEMapabaELopesFPussickFAabyPRomboLComparison of 3, 5 and 7 days' treatment with Quinimax for falciparum malaria in Guinea-BissauTrans R Soc Trop Med Hyg1997914462464[PubMed][Google Scholar]
  • 38. RogierCBrauRTallACisseBTrapeJFReducing the oral quinine-quinidine-cinchonin (Quinimax) treatment of uncomplicated malaria to three days does not increase the recurrence of attacks among children living in a highly endemic area of SenegalTrans R Soc Trop Med Hyg1996902175178[PubMed][Google Scholar]
  • 39. KremsnerPGWinklerSBrandtsCNeiferSBienzleUGraningerWClindamycin in combination with chloroquine or quinine is an effective therapy for uncomplicated Plasmodium falciparum malaria in children from GabonJ Infect Dis19941692467470[PubMed][Google Scholar]
  • 40. Di PerriGOPNardiSDeganelloRAllegranziBBonoraSVentoSConciaEResponse of uncomplicated falciparum malaria to oral chloroquine and quinine in Burundi highlandsActa Trop19987012533[PubMed][Google Scholar]
  • 41. Le JouanMJVTetanyeETranAReyETreluyerJMTodMPonsGQuinine pharmacokinetics and pharmacodynamics in children with malaria caused by Plasmodium falciparumAntimicrob Agents Chemother200549936583662[PubMed][Google Scholar]
  • 42. RocheJBenitoAAyecabaSAmelaCMolinaRAlvarJResistance of Plasmodium falciparum to antimalarial drugs in Equatorial GuineaAnn Trop Med Parasitol1993875443449[PubMed][Google Scholar]
  • 43. RocheJGuerra-NeiraARasoJBenitoASurveillance of in vivo resistance of Plasmodium falciparum to antimalarial drugs from 1992 to 1999 in Malabo (Equatorial Guinea)Am J Trop Med Hyg2003685598601[PubMed][Google Scholar]
  • 44. IbrahimMHElbashirMINaserAAelbasitIAKheirMMAdamILow-dose quinine is effective in the treatment of chloroquine-resistant Plasmodium falciparum malaria in eastern SudanAnn Trop Med Parasitol2004985441445[PubMed][Google Scholar]
  • 45. AchanJTibenderanaJKKyabayinzeDWabwire MangenFKamyaMRDorseyGD'AlessandroURosenthalPJTalisunaAOEffectiveness of quinine versus artemether-lumefantrine for treating uncomplicated falciparum malaria in Ugandan children: randomised trialBMJ2009339b2763[PubMed][Google Scholar]
  • 46. AlecrimMGLacerdaMVMouraoMPAlecrimWDPadilhaACardosoBSBoulosMSuccessful treatment of Plasmodium falciparum malaria with a six-dose regimen of artemether-lumefantrine versus quinine-doxycycline in the Western Amazon region of BrazilAm J Trop Med Hyg20067412025[PubMed][Google Scholar]
  • 47. WHOWorld Malaria Report 20092009
  • 48. KangwanaBBNjoguJWasunnaBKedengeSVMemusiDNGoodmanCAZurovacDSnowRWMalaria drug shortages in Kenya: a major failure to provide access to effective treatmentAm J Trop Med Hyg2009805737738[PubMed][Google Scholar]
  • 49. MillerRSWongsrichanalaiCBuathongNMcDanielPWalshDSKnirschCOhrtCEffective treatment of uncomplicated Plasmodium falciparum malaria with azithromycin-quinine combinations: a randomized, dose-ranging studyAm J Trop Med Hyg2006743401406[PubMed][Google Scholar]
  • 50. McGreadyRChoTSamuelVillegasLBrockmanAvan VugtMLooareesuwanSWhiteNJNostenFRandomized comparison of quinine-clindamycin versus artesunate in the treatment of falciparum malaria in pregnancyTrans R Soc Trop Med Hyg2001956651656[PubMed][Google Scholar]
  • 51. ParolaPRanqueSBadiagaSNiangMBlinOCharbitJJDelmontJBrouquiPControlled trial of 3-day quinine-clindamycin treatment versus 7-day quinine treatment for adult travelers with uncomplicated falciparum malaria imported from the tropicsAntimicrob Agents Chemother2001453932935[PubMed][Google Scholar]
  • 52. NoedlHKrudsoodSChalermratanaKSilachamroonULeowattanaWTangpukdeeNLooareesuwanSMillerRSFukudaMJongsakulKSriwichaiSRowanJBhattacharyyaHOhrtCKnirschCAzithromycin combination therapy with artesunate or quinine for the treatment of uncomplicated Plasmodium falciparum malaria in adults: a randomized, phase 2 clinical trial in ThailandClin Infect Dis2006431012641271[PubMed][Google Scholar]
  • 53. AdamIIbrahimMHAeIAElbashirMILow-dose quinine for treatment of chloroquine-resistant falciparum malaria in Sudanese pregnant womenEast Mediterr Health J2004104-5554559[PubMed][Google Scholar]
  • 54. LellBKremsnerPGClindamycin as an antimalarial drug: review of clinical trialsAntimicrob Agents Chemother200246823152320[PubMed][Google Scholar]
  • 55. PhilipsonASabathLDCharlesDErythromycin and clindamycin absorption and elimination in pregnant womenClin Pharmacol Ther19761916877[PubMed][Google Scholar]
  • 56. McGreadyRAshleyEAMooEChoTBarendsMHutagalungRLooareesuwanSWhiteNJNostenFA randomized comparison of artesunate-atovaquone-proguanil versus quinine in treatment for uncomplicated falciparum malaria during pregnancyJ Infect Dis20051925846853[PubMed][Google Scholar]
  • 57. McGreadyRBrockmanAChoTChoDvan VugtMLuxemburgerCChongsuphajaisiddhiTWhiteNJNostenFRandomized comparison of mefloquine-artesunate versus quinine in the treatment of multidrug-resistant falciparum malaria in pregnancyTrans R Soc Trop Med Hyg2000946689693[PubMed][Google Scholar]
  • 58. QuashieNBDuahNOAbuakuBKoramKAThe in-vitro susceptibilities of Ghanaian Plasmodium falciparum to antimalarial drugsAnn Trop Med Parasitol20071015391398[PubMed][Google Scholar]
  • 59. AdegnikaAABreitlingLPAgnandjiSTChaiSKSchutteDOyakhiromeSSchwarzNGGrobuschMPMissinouMARamharterMIssifouSKremsnerPGEffectiveness of quinine monotherapy for the treatment of Plasmodium falciparum infection in pregnant women in Lambarene, GabonAm J Trop Med Hyg2005732263266[PubMed][Google Scholar]
  • 60. PiolaPNabasumbaCTuryakiraEDhordaMLindegardhNNyehanganeDSnounouGAshleyEAMcGreadyRNostenFGuerinPJEfficacy and safety of artemether-lumefantrine compared with quinine in pregnant women with uncomplicated Plasmodium falciparum malaria: an open-label, randomised, non-inferiority trialLancet Infect Dis20101011762769[PubMed][Google Scholar]
  • 61. ManyandoCMkandawireRPumaLSinkalaMMpabalwaniENjunjuEGomesMRibeiroIWalterVVirtanenMSchliengerRCousinMChipimoMSullivanFMSafety of artemether-lumefantrine in pregnant women with malaria: results of a prospective cohort study in ZambiaMalar J20109249[PubMed][Google Scholar]
  • 62. ColebundersRBahweYNekweiWRyderRPerriensJNsimbaKTurnerAFrancisHLebugheIVan der StuyftPPiotPIncidence of malaria and efficacy of oral quinine in patients recently infected with human immunodeficiency virus in Kinshasa, ZaireJ Infect1990212167173[PubMed][Google Scholar]
  • 63. GreenbergAENsaWRyderRWMediMNzezaMKitadiNBaangiMMalandaNDavachiFHassigSEPlasmodium Falciparum malaria and perinatally acquired human immunodeficiency virus type 1 infection in Kinshasa, Zaire. A prospective, longitudinal cohort study of 587 childrenN Engl J Med19913252105109[PubMed][Google Scholar]
  • 64. SoyinkaJOOnyejiCOOmoruyiSIOwolabiARSarmaPVCookJMEffects of concurrent administration of nevirapine on the disposition of quinine in healthy volunteersJ Pharm Pharmacol2009614439443[PubMed][Google Scholar]
  • 65. SoyinkaJOOnyejiCOOmoruyiSIOwolabiARSarmaPVCookJMPharmacokinetic interactions between ritonavir and quinine in healthy volunteers following concurrent administrationBr J Clin Pharmacol2010693262270[PubMed][Google Scholar]
  • 66. WanwimolrukSKangWCovillePFViriyayudhakornSThitiarchakulSMarked enhancement by rifampicin and lack of effect of isoniazid on the elimination of quinine in manBr J Clin Pharmacol19954018791[PubMed][Google Scholar]
  • 67. PukrittayakameeSPrakongpanSWanwimolrukSClemensRLooareesuwanSWhiteNJAdverse effect of rifampin on quinine efficacy in uncomplicated falciparum malariaAntimicrob Agents Chemother200347515091513[PubMed][Google Scholar]
  • 68. KhooSBackDWinstanleyPThe potential for the interactions between antimalarial and antiretroviral drugsAIDS200519109951005[PubMed][Google Scholar]
  • 69. GasasiraAFKamyaMRAchanJMebrahtuTKalyangoJNRuelTCharleboisEStaedkeSGKekitiinwaARosenthalPJHavlirDDorseyGHigh risk of neutropenia in HIV-infected children following treatment with artesunate plus amodiaquine for uncomplicated malaria in UgandaClin Infect Dis2008467985991[PubMed][Google Scholar]
  • 70. GermanPParikhSLawrenceJDorseyGRosenthalPJHavlirDCharleboisEHanpithakpongWLindegardhNAweekaFTLopinavir/ritonavir affects pharmacokinetic exposure of artemether/lumefantrine in HIV-uninfected healthy volunteersJ Acquir Immune Defic Syndr2009514424429[PubMed][Google Scholar]
  • 71. LesiAMeremikwuMHigh first dose quinine regimen for treating severe malariaCochrane Database Syst Rev20043CD003341[Google Scholar]
  • 72. JonesKLDoneganSLallooDGArtesunate versus quinine for treating severe malariaCochrane Database Syst Rev20074CD005967[Google Scholar]
  • 73. TaylorTEWillsBACourvalJMMolyneuxMEIntramuscular artemether vs intravenous quinine: an open, randomized trial in Malawian children with cerebral malariaTrop Med Int Health19983138[PubMed][Google Scholar]
  • 74. van HensbroekMBOnyiorahEJaffarSSchneiderGPalmerAFrenkelJEnwereGForckSNusmeijerABennettSGreenwoodBKwiatkowskiDA trial of artemether or quinine in children with cerebral malariaN Engl J Med199633526975[PubMed][Google Scholar]
  • 75. GroupTA-QM-aSA meta-analysis using individual patient data of trials comparing artemether with quinine in the treatment of severe falciparum malariaTrans R Soc Trop Med Hyg2001956637650[PubMed][Google Scholar]
  • 76. AcengJRByarugabaJSTumwineJKRectal artemether versus intravenous quinine for the treatment of cerebral malaria in children in Uganda: randomised clinical trialBMJ20053307487334[PubMed][Google Scholar]
  • 77. GomesMFFaizMAGyapongJOWarsameMAgbenyegaTBabikerABaidenFYunusEBBinkaFClerkCFolbPHassanRHossainMAKimbuteOKituaAKrishnaSMakasiCMensahNMrangoZOlliaroPPetoRPetoTJRahmanMRRibeiroISamadRWhiteNJStudy 13 Research GroupPre-referral rectal artesunate to prevent death and disability in severe malaria: a placebo-controlled trialLancet20093739663557566[PubMed][Google Scholar]
  • 78. AchanJTibenderanaJKyabayinzeDMawejjeHMugiziRMpekaBTalisunaAD'AlessandroUCase management of severe malaria--a forgotten practice: experiences from health facilities in UgandaPLoS One201163e17053[PubMed][Google Scholar]
  • 79. AchanJByarugabaJBarennesHTumwineJKRectal versus intravenous quinine for the treatment of childhood cerebral malaria in Kampala, Uganda: a randomized, double-blind clinical trialClin Infect Dis2007451114461452[PubMed][Google Scholar]
  • 80. BarennesHKailouDPussardEMunjakaziJMFernanMSherouatHSandaAClavierFVerdierF[Intrarectal administration of quinine: an early treatment for severe malaria in children?]Sante2001113145153[PubMed][Google Scholar]
  • 81. BarennesHKahiataniDClavierFMeynardDNjifountawaouoSBarennes-RasoanandrasanaFAmadouMSoumanaMMahamansaniAGranicGVerdierF[Rectal quinine, an alternative to parenteral injections for the treatment of childhood malaria. Clinical, parasitological and pharmacological study]Med Trop (Mars)1995554 Suppl9194[Google Scholar]
  • 82. BarennesHKahiataniFPussardEClavierFMeynardDNjifountawouoSVerdierFIntrarectal Quinimax (an association of Cinchona alkaloids) for the treatment of Plasmodium falciparum malaria in children in Niger: efficacy and pharmacokineticsTrans R Soc Trop Med Hyg1995894418421[PubMed][Google Scholar]
  • 83. BarennesHMunjakaziJVerdierFClavierFPussardEAn open randomized clinical study of intrarectal versus infused Quinimax for the treatment of childhood cerebral malaria in NigerTrans R Soc Trop Med Hyg1998924437440[PubMed][Google Scholar]
  • 84. BarennesHBalima-KoussoubeTNagotNCharpentierJCPussardESafety and efficacy of rectal compared with intramuscular quinine for the early treatment of moderately severe malaria in children: randomised clinical trialBMJ2006332754910551059[PubMed][Google Scholar]
  • 85. NdiayeJLTineRCFayeBDieyeelHLDiackPALameyreVGayeOSowHDPilot feasibility study of an emergency paediatric kit for intra-rectal quinine administration used by the personnel of community-based health care units in SenegalMalar J20076152[PubMed][Google Scholar]
  • 86. TheraMAKeitaFSissokoMSTraoreOBCoulibalyDSackoMLameyreVDucretJPDoumboOAcceptability and efficacy of intra-rectal quinine alkaloids as a pre-transfer treatment of non-per os malaria in peripheral health care facilities in Mopti, MaliMalar J2007668[PubMed][Google Scholar]
  • 87. EsamaiFTengeCNAyuoPOOng'orWOObalaAJakaitBA randomized open label clinical trial to compare the efficacy and safety of intravenous quinine followed by oral malarone vs. intravenous quinine followed by oral quinine in the treatment of severe malariaJ Trop Pediatr20055111724[PubMed][Google Scholar]
  • 88. PetersWAntimalarial drug resistance: an increasing problemBr Med Bull1982382187192[PubMed][Google Scholar]
  • 89. WernsdorferWHLandgrafBWiedermannGKollaritschHChloroquine resistance of Plasmodium falciparum: a biological advantage?Trans R Soc Trop Med Hyg19958919091[PubMed][Google Scholar]
  • 90. BjorkmanAPhillips-HowardPAThe epidemiology of drug-resistant malariaTrans R Soc Trop Med Hyg1990842177180[PubMed][Google Scholar]
  • 91. MayxayMBarendsMBrockmanAJaideeANairSSudimackDPongvongsaTPhompidaSPhetsouvanhRAndersonTWhiteNJNewtonPNIn vitro antimalarial drug susceptibility and pfcrt mutation among fresh Plasmodium falciparum isolates from the Lao PDR (Laos)Am J Trop Med Hyg2007762245250[PubMed][Google Scholar]
  • 92. LegrandEVolneyBMeynardJBMercereau-PuijalonOEsterrePIn vitro monitoring of Plasmodium falciparum drug resistance in French Guiana: a synopsis of continuous assessment from 1994 to 2005Antimicrob Agents Chemother2008521288298[PubMed][Google Scholar]
  • 93. TintoHRwagacondoCKaremaCMupfasoniDVandorenWRusanganwaEErhartAVan OvermeirCVan MarckED'AlessandroUIn-vitro susceptibility of Plasmodium falciparum to monodesethylamodiaquine, dihydroartemisinin and quinine in an area of high chloroquine resistance in RwandaTrans R Soc Trop Med Hyg20061006509514[PubMed][Google Scholar]
  • 94. ToureAOKoneLPJambouRKonanTDDembaSBeugreGEKoneM[In vitro susceptibility of P. falciparum isolates from Abidjan (Cote d'Ivoire) to quinine, artesunate and chloroquine]Sante20081814347[PubMed][Google Scholar]
  • 95. PradinesBMabika MamfoumbiMParzyDOwono MedangMLebeauCMourou MbinaJRDouryJCKombilaMIn vitro susceptibility of Gabonese wild isolates of Plasmodium falciparum to artemether, and comparison with chloroquine, quinine, halofantrine and amodiaquineParasitology1998117Pt 6541545[PubMed][Google Scholar]
  • 96. MutandaLNAssessment of drug resistance to the malaria parasite in residents of Kampala, UgandaEast Afr Med J1999768421424[PubMed][Google Scholar]
  • 97. HuttingerFSatimaiWWernsdorferGWiedermannUCongpuongKWernsdorferWHSensitivity to artemisinin, mefloquine and quinine of Plasmodium falciparum in northwestern ThailandWien Klin Wochenschr2010122Suppl 35256[PubMed][Google Scholar]
  • 98. MyintHYTipmaneePNostenFDayNPPukrittayakameeSLooareesuwanSWhiteNJA systematic overview of published antimalarial drug trialsTrans R Soc Trop Med Hyg20049827381[PubMed][Google Scholar]
  • 99. ChongsuphajaisiddhiTSabcharoenAAttanathPIn vivo and in vitro sensitivity of Falciparum malaria to quinine in Thai childrenAnn Trop Paediatr1981112126[PubMed][Google Scholar]
  • 100. WhiteNJLooareesuwanSWarrellDAWarrellMJBunnagDHarinasutaTQuinine pharmacokinetics and toxicity in cerebral and uncomplicated Falciparum malariaAm J Med1982734564572[PubMed][Google Scholar]
  • 101. LooareesuwanSCharoenpanPHoMWhiteNJKarbwangJBunnagDHarinasutaTFatal Plasmodium falciparum malaria after an inadequate response to quinine treatmentJ Infect Dis19901613577580[PubMed][Google Scholar]
  • 102. NewtonPNWardSAngusBJChierakulWDondorpARuangveerayuthRSilamutKTeerapongPSuputtamongkolYLooareesuwanSWhiteNJEarly treatment failure in severe malaria resulting from abnormally low plasma quinine concentrationsTrans R Soc Trop Med Hyg20061002184186[PubMed][Google Scholar]
  • 103. PukrittayakameeSWanwimolrukSStepniewskaKJantraAHuyakornSLooareesuwanSWhiteNJQuinine pharmacokinetic-pharmacodynamic relationships in uncomplicated falciparum malariaAntimicrob Agents Chemother2003471134583463[PubMed][Google Scholar]
  • 104. OnwujekweOKaurHDikeNShuEUzochukwuBHansonKOkoyeVOkonkwoPQuality of anti-malarial drugs provided by public and private healthcare providers in south-east NigeriaMalar J2009822[PubMed][Google Scholar]
  • 105. GaudianoMCDi MaggioACocchieriEAntoniellaEBertocchiPAlimontiSValvoLMedicines informal market in Congo, Burundi and Angola: counterfeit and sub-standard antimalarialsMalar J2007622[PubMed][Google Scholar]
  • 106. BascoLKMolecular epidemiology of malaria in cameroon. XX. Experimental studies on various factors of in vitro drug sensitivity assays using fresh isolates of Plasmodium falciparumAm J Trop Med Hyg2004705474480[PubMed][Google Scholar]
  • 107. LonCTTsuyuokaRPhanouvongSNivannaNSocheatDSokhanCBlumNChristophelEMSmineACounterfeit and substandard antimalarial drugs in CambodiaTrans R Soc Trop Med Hyg20061001110191024[PubMed][Google Scholar]
  • 108. KayumbaPCRishaPGShewiyoDMsamiAMasukiGAmeyeDVergoteGNtawukuliryayoJDRemonJPVervaetCThe quality of essential antimicrobial and antimalarial drugs marketed in Rwanda and Tanzania: influence of tropical storage conditions on in vitro dissolutionJ Clin Pharm Ther2004294331338[PubMed][Google Scholar]
  • 109. MetzgerWMordmullerBGraningerWBienzleUKremsnerPGHigh efficacy of short-term quinine-antibiotic combinations for treating adult malaria patients in an area in which malaria is hyperendemicAntimicrob Agents Chemother1995391245246[PubMed][Google Scholar]
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