Stereoselective pharmacokinetics of amlodipine in elderly hypertensive patients.

Amlodipine is a dihydropyridine calcium antagonist and is widely used for the treatment of cardiovascular diseases. Amlodipine has two stereoisomers [R(+), S(-)], and only the S(-) isomer exerts vasodilating action. In this preliminary study, amlodipine (5 mg) was given to three elderly hypertensive patients once daily for 10 days. Blood samples were obtained, and serum concentrations of R(+)- and S(-)-amlodipine were measured by a gas chromatographic method. The R(+)/S(-) ratio of plasma amlodipine in these elderly subjects was greater than that reported in young subjects. These results suggest that the influence of aging on the pharmacokinetic profiles might differ between the R(+)- and S(-)-isomers of amlodipine.