Enalapril and enalapril-hydrochlorothiazide in the treatment of essential hypertension. The Enalapril-Hydrochlorothiazide in Essential Hypertension Canadian Working Group.

A total of 217 patients with essential hypertension were enrolled by 25 Canadian centers in this double-blind, parallel study to compare the efficacy and safety of enalapril administered alone or in combination with hydrochlorothiazide. After a 4-week placebo period, patients were given 10 mg of enalapril for 2 weeks. At the end of the 2 weeks of therapy, patients were maintained on the same dose of enalapril, titrated to a higher dose of enalapril, or received combination therapy with hydrochlorothiazide if their diastolic blood pressure remained > 90 mmHg. Patients in group 1 received enalapril 10 mg or 20 mg and those in group 2 received enalapril 10 mg alone or combined with hydrochlorothiazide 25 mg. The maintenance phase lasted 8 weeks. A standard mercury sphygmomanometer was used to measure blood pressure at each visit. The mean decrease in supine diastolic blood pressure (SDBP) was 16 mmHg in groups 1 and 2; the mean decrease in supine systolic blood pressure (SSBP) was 19 mmHg in group 1 and 20 mmHg in group 2. Eighty percent of the patients in group 1 and 81% of those in group 2 had an SDBP < or = 90 mmHg at the final visit. To achieve this control, 67% of the patients received enalapril 10 mg and 33% received enalapril 20 mg in group 1. In group 2, 70% of the patients received enalapril 10 mg and 30% received enalapril 10 mg plus hydrochlorothiazide 25 mg. Eighteen patients in group 1 and 17 patients in group 2 experienced one or more minor adverse events. The most frequently reported adverse events were headache, asthenia, abdominal pain, nausea, and dizziness. No major adverse events were observed. We conclude that enalapril used alone reduces blood pressure in the majority of patients with mild to moderate essential hypertension. When blood pressure is not controlled by enalapril alone, hydrochlorothiazide can safely be added to the regimen.