The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage of enalapril maleate, a nonsulfhydryl angiotensin-converting enzyme (ACE) inhibitor, are reviewed. Enalapril is rapidly converted by ester hydrolysis to enalaprilat, a potent ACE inhibitor; enalapril itself is only a weak ACE inhibitor. Enalapril lowers peripheral vascular resistance without causing an increase in heart rate. In patients with congestive heart failure, enalapril has beneficial hemodynamic effects based on reduction of both cardiac preload and afterload. Approximately 60% of a dose of enalapril is absorbed after oral administration. Excretion of enalaprilat is primarily renal. Accumulation of enalaprilat occurs in patients with creatinine clearances less than 30 mL/min. Enalapril 10-40 mg per day orally has shown efficacy comparable to that of captopril in treating patients with mild, moderate, and severe hypertension, hypertension caused by renal-artery stenosis, and in congestive heart failure resistant to digitalis and diuretics. When given alone for hypertension, enalapril has efficacy comparable to that of thiazide diuretics and beta blockers. Side effects observed with enalapril have generally been minor. Captopril-associated side effects such as skin rash, loss of taste, and proteinuria have been observed in a small number of patients receiving enalapril to date; neutropenia less than 300/mm3 has been noted with captopril but not enalapril. The incidence of these side effects has been noted to be greatly decreased in patients on low doses of captopril. Enalapril appears to be similar in efficacy to captopril for treating hypertension and congestive heart failure. Whether enalapril is safer than low-dose captopril in patients at high risk for captopril-associated side effects will require further investigation.
The oral dose response and time course of action of indacrinone was compared with that of furosemide in six healthy men on a sodium and potassium-controlled diet. The single doses were 5, 10, 20, 40, and 80 mg indacrinone and 20, 40, and 80 mg furosemide. Diuretic, natriuretic, and kaliuretic effects revealed that indacrinone was more potent, had a longer duration of action, and induced a greater sodium for equivalent potassium loss during its period of peak activity than furosemide. During the 8 hr after drug, all doses of indacrinone decreased serum uric acid levels and increased uric acid clearance while furosemide generally increased serum uric acid and decreased uric acid clearance. After 24 hr, serum uric acid and uric acid clearance were the same for the two drugs. A rise in plasma renin activity was observed 2 hr after an 80-mg dose of furosemide but not after indacrinone.
The serum concentrations and β-blockade after dermal application of timolol ointment were evaluated in six healthy men (21–31 years old; 74–82 kg). Two patches (25 cm2) containing placebo and either 30 (n = 2) or 60 mg (n = 4) timolol base were randomly applied to the chest for 30 h. Serial serum concentrations of timolol were measured by a radioligand receptor assay. Bicycle ergometry, at a predetermined workload, was performed before and at 3, 8, 24, and 48 h after patch application; mean ± SD heart rates (beats/min) at these times were 167 ± 2. 158 ± 7, 125 ± 7, 120 ± 5, and 150 ± 5 (last 3 values: p < 0.05 from pretreatment), and β-blockade was evident in all subjects. Measurable serum concentrations in the therapeutic range were achieved in all subjects. The change in exercise-induced heart rate (y) was closely related to log timolol serum concentration (x) (y = −36 × −5.3: r = −0.92: p < 0.001). Based on the amount of timolol in the residual ointment. 50–60% of the original timolol dosage was delivered from the patch. Skin irritation under the patch compared with placebo was minimal. Further studies are warranted to assess the potential clinical utility of transdermal timolol.
