Pharmacokinetic behaviour of R-(+)- and S-(-)-amlodipine after single enantiomer administration

Amlodipine, 3-ethyl 5-methyl-2-[(2-aminoethoxymethyl]-4-(2-chlorophenyl)-1,4-dihydro-6-methyl-3,5-pyridinedicarboxylate, is a chiral calcium antagonist, currently on the market and in therapeutic use as a racemate. The pharmacokinetic behaviour of R-(+)- and S-(-)-amlodipine after single enantiomer administration to healthy male human volunteers together with comparative administration of the racemic mixture of both enantiomers were studied. Plasma levels were studied as a function of time and assayed using an enantioselective chromatographic method (coupled chiral and achiral HPLC) with on-line solid-phase extraction and UV absorbance detection. The method was validated separately for the R-(+)- and S-(-)-enantiomer, respectively. Results of the study indicate that the pharmacokinetic behaviour of R-(+)- and S-(-)-amlodipine after single enantiomer administration is comparable to that of each enantiomer after administration of the racemate. No racemization occurs in vivo in human plasma after single enantiomer administration. (C) 1997 Elsevier Science B.V.