There has been a resurgence of interest in the use of colistin for the treatment of multidrug-resistant Gram-negative bacterial infections. A more favorable infection outcome is observed when colistin is used in combination with carbapenems. We present a patient with severe New Delhi metallo-β-lactamase-1 Escherichia coli infection who developed convulsions rapidly followed by acute respiratory muscle weakness and apnoea during treatment with colistin and meropenem. Chromatographic assay showed a "trough" colistin level that was approximately fourfold higher than previously reported maximum steady-state colistin plasma levels in critically ill patients. The patient's renal clearance never necessitated dose adjustments, suggesting that the observed high plasma colistin level might be due to impaired non renal elimination. Although meropenem itself has very low neurotoxic potential, its concomitant use with colistin may have elicited colistin neurotoxicity.