The effects of missed doses of amlodipine and losartan on blood pressure in older hypertensive patients.

This randomized, double-blind, parallel-group, multicenter study compared the efficacy of amlodipine and losartan in an older hypertensive population, focusing on therapeutic coverage in the case of missed doses. Following a 4-week, single-blind, placebo washout period, 211 patients were randomly assigned to receive either 5 mg of amlodipine once daily or 50 mg of losartan once daily. Doses were doubled after 6 weeks of treatment if the diastolic blood pressure exceeded 90 mm Hg. After the 12-week treatment period, patients received the placebo for 2 days (drug holiday) to simulate two missed doses of antihypertensive medication. Twenty-four-hour ambulatory blood pressure monitoring was conducted at the end of the placebo washout period (baseline), upon completion of the 12-week treatment period (steady state), and after the 2-day drug holiday. Amlodipine was more effective than losartan in reducing patients' 24-h ambulatory blood pressure at the steady-state sampling time. The increases in 24-h blood pressure during the drug holiday averaged 6±2/2±1 mm Hg (P<0.0001) in the amlodipine group and 3±2/2±1 mm Hg (P<0.0001) in the losartan group. The rise in systolic pressure was greater in patients on amlodipine than in those on losartan (P<0.0001). For diastolic pressure, the changes did not differ. Owing to the lower pressure during treatment, patients in the amlodipine group remained at a significantly lower blood pressure level after the 2-day drug holiday. Amlodipine was more effective than losartan in lowering blood pressure and in maintaining blood pressure control after two missed doses, and the difference was most significant for systolic blood pressure.