Pharmacological characteristics of the stereoisomers of carvedilol.

The racemic compound carvedilol possesses two complementary pharmacological effects, vasodilation and beta-blockade. The R- and S-enantiomers of carvedilol and the racemate were investigated with respect to the beta-blocking, vasodilating, and hypotensive actions. In agreement with results obtained with other beta-blockers, only the S-enantiomer of carvedilol exerts beta-blocking effects. In contrast, no substantial difference between the enantiomers could be seen with respect to alpha-blockade. The greater hypotensive activity of S-carvedilol may be attributed to beta-blockade, which inhibits counter-regulatory mechanisms provoked by vasodilation. From these results it is concluded that there is a rationale for using carvedilol as the racemate. Using the S-enantiomer would lead to relatively strong beta-blockade with only a weak vasodilating effect. The R-enantiomer alone would act only as a hypotensive agent without beta-blockade.