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, administered as a single daily dose of 0.6 mg, with the angiotensin-converting enzyme inhibitor enalapril (20 mg o.d.) in patients with mild to moderate essential hypertension.

Methods: A total of 154 patients were enrolled and randomized to placebo (n = 50), moxonidine (0.2 mg o.d.; n = 51) or enalapril (5 mg o.d.; n = 53) for 2 weeks. Dosages were then increased to moxonidine 0.6 mg o.d. or enalapril 20 mg o.d. for a further 6 weeks. Blood pressure responses to therapy were measured using conventional office techniques and by 24-h ambulatory blood pressure monitoring.

Results: The average reduction in sitting blood pressure with moxonidine was similar to that achieved with enalapril (24.9 +/- 20.7/13.2 +/- 8.4 mmHg vs 21.9 +/- 17.1/11.9 +/- 7.5 mmHg, respectively) and significantly superior to that seen with placebo (1.2 +/- 14.4/2.3 +/- 7.0 mmHg; p < 0.001). Reductions in blood pressure after 8 weeks of treatment were as follows: moxonidine, from 166.2 +/- 15.5/101.3 +/- 4.0 to 141.2 +/- 15.7/88.1 +/- 7.7mmHg; enalapril, from 165.4 +/- 14.3/101.1 +/- 4.4 to 143.5 +/- 12.7/89.2 +/- 7.4 mmHg; and placebo, from 162.5 +/- 14.4/99.9 +/- 3.9 to 161.3 +/- 17.9/97.6 +/- 6.6 mmHg. Both moxonidine and enalapril produced sustained reductions in blood pressure during 24-h recording (p < 0.01 for overall effect of either drug vs placebo). Average 24-h blood pressure was reduced from 149.8 +/- 14.3/92.2 +/- 7.0 to 134.0 +/- 13.1/82.3 +/- 8.9 mmHg with moxonidine and from 146.5 +/- 13.0/ 92.5 +/- 7.2 to 131.1 +/- 11.0/82.1 +/- 8.8 mmHg with enalapril; the change with placebo was small (from 147.3 +/- 13.3/90.0 +/- 6.2 to 144.8 +/- 12.9/89.5 +/- 8.0 mmHg). Both drugs were generally well tolerated. No patients withdrew from the study because of drug-attributed adverse events.

Conclusion: Moxonidine 0.6 mg o.d. and enalapril 20 mg o.d. have similar antihypertensive efficacy.