Bioanalytics of nimodipine--an overview of methods

The analytical test procedures currently established for the determination of the dihydropyridine calcium antagonist nimodipine in biological fluids are presented. Method of choice which has been dominantly used in pharmacokinetic investigations and drug interaction studies is gas chromatography with electron-capture detection (GC-ECD) subsequent to simple toluene extraction. The limit of quantification of 0.1 ng/ml in plasma conveniently allows to follow concentration/time profiles in the nano/subnanogram per ml-range after therapeutic doses. If not restricted by its markedly higher limit of quantification of approx. 1-5 ng/ml, high-performance liquid chromatography with either UV- or amperometric detection may be an attractive alternative for therapeutic drug monitoring or compliance control. A combined approach of HPLC and GC--chiral stationary-phase HPLC with GC-MS as off-line detection mode--has proven adequate and efficient to obtain pharmacokinetic data for nimodipine enantiomers after administration of the racemic drug.