Key result
Levo-verapamil is ~20-fold more potent than dextro-verapamil at prolonging AV nodal conduction and SNRT.
Why the study?
The electrophysiologic effects of dextro- and levo-verapamil on SA and AV node function in humans were not fully characterized, including their relative potency.
Supports stereoselective nodal effects of verapamil; extends prior data to humans yet leaves clinical translation open.
The electrophysiologic effects of dextro (d)- and levo (l)-verapamil on sinoatrial (SA) and atrioventricular (AV) node function were studied in ten patients undergoing electrophysiologic evaluation of their supraventricular tachyarrhythmias. Both isomers elicited a significant prolongation of sinus node recovery time (SNRT) and AH interval. No difference between d- and l-verapamil regarding the magnitude of the effects were observed. However, 50 mg d-verapamil was required to elicit the same electrophysiologic effects as 5 mg l-verapamil. The d- and l-verapamil plasma concentrations associated with the maximum effect on AH interval and SNRT showed a more than 20-fold difference (d: 380 ng/ml; l: 19 ng/ml). These data demonstrate that both verapamil isomers possess qualitatively similar slow channel blocking effects on the SA and AV node in humans, but the l isomer is 20 times more potent than the d isomer.
No takes yet. Share an insight, caveat, or question.
Echizen et al. (1988) studied Supraventricular tachyarrhythmias (n=10). Dextro-verapamil and levo-verapamil vs. Intra-individual comparison (isomers compared to each other) was evaluated on Maximum effect on AH interval and sinus node recovery time (SNRT). Both verapamil isomers prolonged sinus node recovery time and AH interval, but levo-verapamil was 20 times more potent than dextro-verapamil in humans.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: