Simultaneous quantification of mefloquine (+)- and (−)-enantiomers and the carboxy metabolite in dried blood spots by liquid chromatography/tandem mass spectrometry

• Simultaneous quantification of both mefloquine enantiomers and the main metabolite.
• The method can be used for dried blood spots or for plasma samples.
• The method is suitable for pharmacokinetic analysis in large cohorts.
• The zwitterionic chiral column CHIRALPAK® ZWIX(−) showed high robustness.

Mefloquine (MQ), a racemic mixture of (+)-(11S,12R)- and (−)-(11R,12S)-MQ, has been used for treatment and prophylaxis of malaria for almost 30 years. MQ is metabolized by the cytochrome P450 3A subfamily to 4-carboxymefloquine (CMQ), which shows no antimalarial activity in vitro. Highly stereospecific pharmacokinetics of MQ have been reported, although with contradictory results. This might be due to incorrect assignment of the absolute configuration as shown only recently. Gastrointestinal as well as neuropsychiatric adverse events were described after prophylaxis and treatment with MQ. Data are indicating that the tolerability of the enantiomers may vary considerably. An involvement of the main metabolite CMQ in the development of neuropsychiatric adverse events has also been supposed. Due to these inconsistent results we established a novel liquid chromatography/tandem mass spectrometry (LC–MS/MS) method for the simultaneous quantification of MQ enantiomers and the metabolite CMQ to investigate the attribution of efficacy and adverse effects to the single enantiomers as well as the main metabolite. Separation of the MQ enantiomers was achieved on a quinidine-based zwitterionic chiral stationary phase column, CHIRALPAK® ZWIX(−) (3.0 × 150 mm, 3 μm) in an isocratic run using a pre-mixed eluent consisting of methanol/acetonitrile/water (49:49:2 v/v) with 25 mM formic acid and 12.5 mM ammonium formate. We used stable isotope-labelled analogues as internal standards. The method was validated according to the FDA guidelines. With a linear calibration range from 5 to 2000 nM for the MQ enantiomers and from 13 to 2600 nM for CMQ respectively, the method was successfully applied to dried blood spot (DBS) samples from patients under prophylactic MQ treatment. The method was also applicable for plasma samples.