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.
An 8-week, double-blind, randomized, placebo- controlled study involving 140 outpatients with mild-to- moderate essential hypertension.
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.
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.
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.