Antihypertensive efficacy and orthostatic tolerance of bunazosin vs nitrendipine: a multicentre double-blind...

A multicentre double-blind randomized controlled study was conducted in 358 patients with mild to moderate essential hypertension. The goal was to compare the antihypertensive efficacy, tolerability, and in particular postural hypotension of the alpha 1-adrenoreceptor blocker bunazosin with the calcium channel blocker nitrendipine. Both treatment groups had comparable baseline blood pressure (BP) values, namely diastolic BP (DBP) of 103.8 +/- 5.6 mm Hg in the bunazosin group, and 103.4 +/- 6.0 mm Hg in the nitrendipine group, respectively. Baseline systolic BPs (SBP) were 149.7 +/- 14.4 mm Hg (bunazosin) and 149.2 +/- 14.3 mm Hg (nitrendipine). After 12 weeks of therapy, reduction of DBP (-6.1 +/- 11.7 mm Hg on bunazosin vs -6.9 +/- 9.9 mm Hg on nitrendipine; P = n.s.), and SBP (-4.4 +/- 14.3 mm Hg on bunazosin vs -7.0 +/- 14.4 mm Hg on nitrendipine; P = n.s.) was similar in both groups. During a provocative orthostatic tolerance test after the first dose, the incidence of prae-collapses (ie termination of the test due to orthostatic complaints) was higher on bunazosin (17 vs 2; P < 0.05) but orthostatic dysregulation symptoms (symptom score 1.37 on bunazosin vs 0.95 on nitrendipine; n.s.) and collapses (four on bunazosin vs one on nitrendipine; n.s.) occurred to a similar extent in both treatment groups. Three and 9 weeks after treatment, no increased susceptibility to orthostatic stress compared to baseline could be found in either group. Under daily life conditions, the frequency of orthostatic dysregulation was identical in both groups (0.8%). Bunazosin, however, was far better tolerated with 43.8% of the patients complaining of adverse events as opposed to 63.6% on nitrendipine (P < 0.001). The rate of early discontinuations due to adverse events was only 1.3% on bunazosin compared to 13.6% on nitrendipine (P < 0.001). In conclusion, bunazosin has a similar antihypertensive efficacy as nitrendipine. Despite an initially higher susceptibility to orthostatic stress under a provocative manoeuver, bunazosin evoked the same low incidence of orthostatic dysregulation symptoms as nitrendipine under daily life conditions, but was significantly better tolerated than nitrendipine.