Serum concentration and effects of a single dose of enalapril maleate in patients with essential hypertension.

The antihypertensive effect of a non-sulfhydryl, long acting ACE (angiotensin converting enzyme) inhibitor, MK-421, was evaluated by administering a single dose of 10 mg to 13 patients with mild to moderate essential hypertension. The pharmacokinetic profile of MK-421 and its potent active metabolite, MK-422, was also assessed, together with the effect on the various components of the renin-angiotensin system. A single dose of MK-421 produced a significant fall in MBP from 2 to 24 hours post-drug. As could be expected, plasma ACE activity was suppressed up to 24 hours after MK-421. The half-life of MK-422, Cmax and [AUC]24(0) of MK-421 and MK-422 were measured. No significant change in plasma bradykinin or urinary excretion rate of kallikrein was observed, whereas a slight increase was observed in the urinary excretion rate of kinins after MK-421 in 8 patients. Significant correlations were observed between pretreatment PRA levels and the maximum fall in MBP.