Plasma levels of (+)- and (-)-nilvadipine after oral dosing with racemic (+)-nilvadipine in man.

The plasma levels of (+)- and (-)-nilvadipine 1 h after an oral dose of racemic (+)-nilvadipine 4 mg in sixteen healthy volunteers were studied to find the extent of variation between (+)- and (-)-nilvadipine plasma levels. Additionally the pharmacokinetic profiles of the enantiomers in the plasma up to 12 h after dosing were examined in three subjects. The plasma levels of the (+)- and (-)-nilvadipine in the three subjects peaked at 0.5-1 h, and the maximum concentration and the area under the plasma concentration-time curve of the more potent (+)-enantiomer were 2.38-3.18 and 2.27-3.10 times, respectively, higher than those of its optical antipode. The half-lives of the enantiomers were mostly similar. In the sixteen subjects, the ratio between (+)- and (-)-nilvadipine levels 1 h after dosing with racemic (+)-nilvadipine were from 1.77 to 3.65.