Efficacy of sustained-release verapamil: automatic ambulatory blood pressure monitoring

The potential antihypertensive effect of sustained-release (SR) verapamil was compared to immediate-release (IR) verapamil in a group of patients with essential hypertension. All patients were withdrawn from their previous antihypertensive medication(s) and were entered into an open-label IR verapamil study (dose varying from 80 to 120 mg TID). Patients were subsequently randomized in a double-blind fashion to continue the same dose of IR verapamil or an equivalent dose of SR verapamil. Automatic ambulatory blood pressure recordings were carried out with a Del Mar Avionics PIII Unit in eight patients who were randomized into the SR group. An initial 24-hour recording was performed on the IR verapamil group during the open-label phase and repeated following treatment with SR verapamil. Mean 24-hour systolic blood pressure (SPB) and diastolic blood pressure (DBP) were 143 +/- 18 mmHg and 89 +/- 6 mmHg, respectively, on IR verapamil and 142 +/- 22 and 90 +/- 6 mmHg, respectively, on SR verapamil. There were no statistically significant differences noted between the two groups. Mean SBP and DBP varied similarly during waking and sleeping periods with IR and SR verapamil: With IR verapamil, SBP was 139 +/- 18 and 124 +/- 20 mmHg and DBP was 92 +/- 11 and 84 +/- 13 mmHg during waking and sleeping hours, respectively; with SR verapamil, SBP was 138 +/- 21 and 122 +/- 22 mmHg and DBP 92 +/- 10 and 80 +/- 10 mmHg during waking and sleeping hours, respectively. DBP was less than or equal to 90 mmHg in approximately 70% and 60% of patients in the IR verapamil and SR verapamil groups, respectively. Trough plasma levels of 92 +/- 44 and 67 +/- 32 ng/ml were measured by HPLC, 2 and 4 weeks, respectively, after treatment with IR verapamil. During a similar time interval, SR verapamil revealed plasma levels of 64 +/- 59 and 92 +/- 57 ng/ml, respectively. No correlation between change in DBP and plasma level of verapamil was demonstrated. No significant change in heart rate was observed during the 4-week period. In summary, verapamil is an effective antihypertensive medication and can be administered once a day as a slow-releasing preparation; it is most useful in patients in whom adrenergic blocking drugs are indicated.