The effects of missing a dose of enalapril versus amlodipine on ambulatory blood pressure.

OBJECTIVE: To compare the antihypertensive actions of amlodipine and enalapril in a double-blind, randomized, parallel-group study during treatment and when missing a dose. METHOD: After a single-blind run-in 4-week placebo period, patients were randomly allocated to receive enalapril (15 patients) or amlodipine (15 patients). Patients received active treatment for 4 weeks (20 mg enalapril or 5 mg amlodipine). For those with sitting diastolic office pressure not below 90 mmHg the dosage was doubled and continued up to week 12. Ambulatory blood pressure monitoring was performed at the end of the placebo run-in period for 24 h and at the end of week 12 for 48 h; in this case, patients took the active tablet at 0700 h of the first day and a placebo tablet on the next day to stimulate a missing dose in a single-blind manner. RESULTS: Of the patients, 60% had office blood pressure controlled by enalapril therapy and 80% had amlodipine therapy. The average dosage was 30.7 mg a day for enalapril and 7.3 mg a day for amlodipine. Reductions in blood pressures were higher for the amlodipine group. Ambulatory blood pressure measurement shows a reduction in systolic and in diastolic blood pressure during the 24 h when patients from both groups were receiving their medication with respect to placebo values. During the second day of ambulatory blood pressure recording, when the patient had taken a placebo tablet instead of an active one, the antihypertensive effect was progressively lost with enalapril, but not with amlodipine. CONCLUSION: Enalapril and amlodipine reduced ambulatory systolic and diastolic blood pressure during treatment; however, when patients missed an enalapril dose, control of blood pressure was progressively lost, whereas patients receiving amlodipine maintained their blood pressure under control up to 48 h after the last dose.