Plasma enalapril levels and hormonal effects after short- and long-term administration in essential hypertension.

Enalapril lowers blood pressure both acutely and during long-term therapy in patients with essential hypertension. After a single 10 mg dose of enalapril a close relationship between plasma enalaprilic acid (MK-422) levels, angiotensin converting enzyme (ACE) inhibition and the acute hypotensive and hormonal effects was demonstrated. During long-term administration of enalapril, a similar relationship between the plasma enalaprilic acid level, ACE inhibition and the hypotensive effect was shown, although the dose-response curve for plasma enalaprilic acid to ACE inhibition was displaced to the right compared to the acute dose-response curve. Several weeks' administration of enalapril was needed to reach stable plateau levels of plasma enalaprilic acid and ACE inhibition. During long-term treatment with enalapril in essential hypertension, there was sustained inhibition of ACE and the associated hormonal changes.