Alpha-adrenergic blockade for variant angina: a long-term, double-blind, randomized trial.

Recent reports have shown that beta-adrenergic blockade may exacerbate variant angina. On theoretical grounds, alpha-adrenergic blockade may be beneficial in these patients. To test this hypothesis, we assessed the efficacy of prazosin, an alpha-adrenergic blocking agent, in six men, mean age 49 years, with variant angina. Prazosin, 14.0 +/- 2.4 mg/day (mean +/- SD) in three equal doses, was compared with placebo in a double-blind, randomized, double-crossover trial lasting 4 1/2 months: 2 weeks of open-label prazosin followed by four 1-month periods of blinded alternating therapy. No other vasoactive medications were administered during the study. Prazosin reduced sitting systolic arterial pressure from 145 +/- 18 to 127 +/- 16 mm Hg (p = 0.02), but exerted no effect on diastolic arterial pressure or heart rate. Prazosin did not change the weekly number of episodes of chest pain (2.5 +/- 2.3 with placebo vs 3.1 +/- 3.0 with prazosin, NS), nitroglycerin tablets used (3.9 +/- 3.7 with placebo vs 4.6 +/- 4.2 with prazosin, NS), or transient ST-segment deviations (by calibrated two-channel Holter monitoring for 24 hours/week throughout the study) (6.5 +/- 10.1 with placebo vs 11.8 +/- 17.4 with prazosin, NS). During prazosin therapy, three patients had orthostatic dizziness and one patient had headache. Thus, in a long-term, randomized, double-blind trial, prazosin exerted no obvious beneficial effect in patients with variant angina.