Pharmacokinetics of prenylamine racemate and enantiomers in man.

Pharmacokinetics of racemic prenylamine were investigated in 6 healthy volunteers. Plasma levels were determined by gas chromatography/mass spectrometry. Concentration-time profiles were analyzed both by compartment-dependent and compartment-independent pharmacokinetic models. Terminal elimination half-life was 14.1 h (SD: 6.9 h). The apparent total clearance was 5.8 l/min. Mean residence time of racemic prenylamine was found to be 14.7 h (SD: 3.8 h). The relative bioavailability of prenylamine (Segontin 100) was 82.2% (SD: 9.9%) determined in six healthy volunteers. The volunteers received simultaneously the film tablet and 100 mg racemic dideuteroprenylamine as an aqueous solution of the lactate. This procedure is known to exclude intraindividual changes in absorption, first-pass metabolism or volume of distribution that might occur on sequential administration. The absolute bioavailability was estimated to be in the order of 15%. In a pilot study the pharmacokinetics of the enantiomers were investigated in 2 healthy volunteers. S-(+)-prenylamine was eliminated considerably faster from plasma than R-(-)-prenylamine suggesting a stereoselective metabolism. The AUC of the (+)-enantiomer was 20% of that of the R-(-)-prenylamine.