Effect of ‘Drug Holiday’ on Blood Pressure Control: A Randomized Double-Blind Comparative Trial of Amlodipine versus Felodipine Extended Release in Chinese Patients with Mild to Moderate Essential Hypertension

Objective: To compare the antihypertensive effect and safety of amlodipine and felodipine extended release (ER). Methods: Seventy-six patients with mild to moderate hypertension were randomized to two groups in a double-blind manner. One group was treated with amlodipine 5.0–10.0 mg/day (group 1), and the other group with felodipine ER 5.0–10.0 mg/day (group 2), for 12 weeks. Twenty-four-hour ambulatory blood pressure (ABP) monitoring at baseline and after treatment was used to evaluate drug efficacy and blood pressure (BP) changes during a ‘drug holiday’ (48 h). Results: Diastolic BP was reduced in the amlodipine group by 15.1 mm Hg (to a final BP of 84.8 mm Hg) and in the felodipine ER group by 15.3 mm Hg (to a final BP of 85.0 mm Hg). Efficacy was considered to be achieved in 83.8% of patients in group 1 and in 87.9% of patients in group 2 (not significant). The number of patients controlled at the starting dose was 28 in group 1 and 19 in group 2 (p < 0.01). In group 1, BP remained below 140/90 mm Hg 24–48 h after the missed dose, and 24-hour ABP was not significantly different from that before the missed doses. In group 2, BP was above 140/90 mm Hg after the missed dose, and both BP and 24-hour ABP were statistically significantly higher than those before the missed doses. Adverse reactions were infrequent in both groups. Conclusions: Both amlodipine and felodipine ER are effective, safe, reliable and well tolerated in the treatment of mild to moderate essential hypertension. BP was well controlled in group 1 24–48 h after the missed dose. The fluctuation of BP in group 2, however, was significantly worse than that in group 1.