A chiral LC–MS/MS method for the stereospecific determination of efonidipine in human plasma

•The first chiral method for quantification of efonidipine enantiomers in human plasma was developed.•The method utilized a chiral stationary phase column, one-step LLE, and good sensitivity.•The method has been validated following bioanalytical validation guidelines.•The method was applied to the PK of efonidipine enantiomers in human subject for the first time.

Efonidipine hydrochloride is a new generation dihydropyridine Ca2+ channel blocker designed to inhibit both T-type and L-type Ca2+ channels. Efonidipine possesses a chiral carbon and is clinically administered as a racemate. In the present study, an enantioselective and sensitive LC–MS/MS method of determining efonidipine enantiomers in human plasma was developed and validated to characterize the stereoselective pharmacokinetics. Plasma samples were processed by liquid-liquid extraction (LLE). Chiral separation was optimized on a CHIRALPAK® ID column using an isocratic mobile phase of acetonitrile/water (60:40, v/v). Detection was using MS in multiple reaction monitoring (MRM) mode, using the transitions of m/z 632.3 → 91.1 for efonidipine enantiomers, and m/z 493.3 → 117.2 for cilnidipine (internal standard). The calibration curves were linear over 0.100–20.0 ng/mL for each enantiomer. The lower limit of quantification (LLOQ) for each enantiomer was established at 0.100 ng/mL. Intra- and inter-day precisions were less than 12.1% for each enantiomer in terms of relative standard deviation (RSD), and accuracies were between −5.0% and 5.0% in terms of relative error (RE) for each enantiomer. No chiral inversion was observed during sample storage, preparation procedure and analysis. The validated method was successfully applied to a stereoselective pharmacokinetic study of efonidipine in healthy subjects after oral administration of 40 mg (20 mg × 2) efonidipine hydrochloride tablets.

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