Figure 1.

Concentration-dependent inhibitory effects of (a) verapamil and (b) diltiazem on formation of 3′-hydroxy-(▪) and 6β-exomethylene-simvastatin (•) in human liver microsomes. Verapamil or diltiazem were either coincubated with simvastatin and microsomes before the reaction was initiated with an NADPH-generating system (solid symbols) or preincubated with microsomes and an NADPH-generating system for 30 min at 37 °C before addition of simvastatin (open symbols). Values are expressed as mean (± s.d., n = 3 livers) percentage of the control in the absence of inhibitor.