Enalapril: a new angiotensin converting enzyme inhibitor

Enalapril maleate is a new angiotensin converting enzyme inhibitor marketed in the U.S. by Merck Sharp and Dohme. It has been demonstrated to actively interfere with the renin-angiotensin-aldosterone system. This is reflected by both hemodynamic (decreased blood pressure) and humoral (increased plasma renin, angiotensin I, and decreased angiotensin II) responses to enalapril therapy. Activity in the kallikrein-bradykinin system is still controversial. Enalapril maleate is a prodrug which is quickly absorbed, hydrolyzed by the liver to the active metabolite enalaprilic acid, and excreted 33 percent in the bile and 61 percent in the urine. The therapeutic dosage range is 10-40 mg/d, maximum of 40 mg, given once or twice daily. The onset and duration of action are dose related. Vertigo and headache have been the most commonly reported side effects. Clinical comparison of enalapril to hydrochlorothiazide, beta-adrenergic blockers, and captopril find it efficacious in the treatment of essential hypertension. Efficacy in treating congestive heart failure and hypertension secondary to renal artery stenosis has also been demonstrated for both angiotensin converting enzyme inhibitors. The overall efficacy and safety of enalapril and captopril appear equivalent when used at low doses in patients with uncomplicated hypertension.