Placebo-controlled comparison of the efficacy and tolerability of once-daily moxonidine and enalapril in mild-to-moderate essential hypertension

OBJECTIVES: To compare the antihypertensive efficacy and tolerability of the imidazoline I1 receptor agonist moxonidine, a centrally acting antihypertensive, with the angiotensin converting enzyme inhibitor enalapril. DESIGN: An 8-week, double-blind, randomized, placebo-controlled study involving 140 outpatients with mild-to-moderate essential hypertension. METHODS: Outpatients with WHO stage I or II hypertension were enrolled in the study. After a 4-week placebo-controlled stabilization phase patients were allocated randomly to placebo, 0.2 mg moxonidine once a day or 5 mg enalapril once a day for 2 weeks. Dosages were then doubled to 0.4 mg moxonidine once a day or 10 mg enalapril once a day for a further 6 weeks. Blood pressure responses to therapy were measured by conventional office techniques and by 24 h ambulatory blood pressure monitoring. RESULTS: The mean reduction in sitting blood pressure with moxonidine was similar to that with enalapril (19.5 +/- 16.0/12.3 +/- 8.7 versus 18.9 +/- 13.7/11.8 +/- 8.0 mmHg) and significantly superior to that with placebo (-4.6 +/- 12.3/-4.7 +/- 6.8 mmHg, P< 0.001). In addition to reducing blood pressure during conventional measurements, moxonidine administration reduced blood pressure throughout 24 h ambulatory measurements. The trough:peak ratio for moxonidine was 0.7. Both moxonidine and enalapril were tolerated well. CONCLUSIONS: Moxonidine is an effective and well-tolerated antihypertensive, at least as good as other established forms of antihypertensive medication. The trough:peak ratio of 0.7 indicates that the drug will be effective administered once a day.