Comparison of the effects of a 7-day period of non-compliance on blood pressure control using three different antihypertensive agents

OBJECTIVES: To compare blood pressure control during 7 days of drug omission in patients taking bendroflumethiazide 2.5 mg, nifedipine LA 30 mg or enalapril 20 mg once daily and, secondarily, to measure patient compliance. METHODS: Twenty-four patients with hypertension were assigned, in a random crossover fashion, to a sequence of bendroflumethiazide, nifedipine LA and enalapril, each for 4 weeks, followed by a 1-week period of dose omission. The patients measured their own blood pressure daily using an Omron 705CP monitor. Differences in blood pressure from baseline (mean blood pressure during week 4 on treatment) and the week of dose omission were compared between the three drugs. Patient compliance was measured using pill counts and the Medication Event Monitoring System. RESULTS: Bendroflumethiazide maintained blood pressure control during drug omission for longer than enalapril or nifedipine LA. The magnitudes of the increase in systolic blood pressure (SBP) between baseline and day 7 off treatment were 7.0, 12.2 and 9.7 mmHg for bendroflumethiazide, nifedipine LA and enalapril, respectively. For diastolic blood pressure (DBP), the values were 2.9, 5.3 and 7.3 mmHg for bendroflumethiazide, nifedipine LA and enalapril, respectively. Differences in SBP between bendroflumethiazide and the comparator drugs occurred at day 2 off treatment. Differences in DBP between bendroflumethiazide and nifedipine were apparent on days 2 and 3 off treatment. Differences in DBP between bendroflumethiazide and enalapril were apparent on days 2, 3, 4 and 5 off treatment. Patient compliance throughout the study was high in terms of both taking the medication when required and omitting the medication when required. CONCLUSIONS: Bendroflumethiazide maintained blood pressure control during a period of drug omission better than nifedipine or enalapril.