Felodipine versus prazosin as an addition to a beta-blocker in the treatment of essential hypertension. The Australian Multicentre Study.

The efficacy and tolerability of felodipine and prazosin were compared in a double-blind randomised parallel group study of 100 patients with moderately severe essential hypertension, treated concomitantly with a beta-blocking drug. After a 2- to 8-week run in phase (beta-blocking drug plus placebo), patients with a diastolic blood pressure greater than or equal to 95mm Hg were randomly given felodipine (n = 50) or prazosin (n = 50). After an initial dose of either felodipine 2.5mg bid or prazosin 0.5mg bid for 3 days, the drugs were titrated at 2-week intervals (felodipine 5, 10, 20mg bid, prazosin 1, 2, 4mg bid) if the supine diastolic blood pressure was greater than or equal to 90mm Hg. Treatment was continued for 8 weeks. Baseline supine blood pressures of each group were similar (177/104mm Hg, felodipine; 176/103mm Hg, prazosin). At week 6, supine blood pressures in the felodipine group were 144/82mm Hg and 161/90 in the prazosin group. The reductions in systolic and diastolic blood pressures were significantly greater for the felodipine group than the prazosin group in both the supine and standing positions at all visits after baseline. At 8 weeks, supine diastolic blood pressure less than 90mm Hg was achieved in more patients in the felodipine (36/47) than in the prazosin group (20/43, p less than 0.01). The total number of adverse reactions was similar in both groups. During active therapy, a greater number of patients experienced vascular adverse reactions (oedema and flushing) with felodipine (23) than with prazosin (12). Most events were mild and did not necessitate withdrawal from therapy. There were no clinically significant changes in laboratory variables in either treatment group. Felodipine was an effective, well tolerated hypotensive agent when used concomitantly with a beta-blocking drug. In the doses used it was more effective than prazosin at reducing blood pressure.