Orthostatic hypotension: how to avoid it during antihypertensive therapy

This was a double-blind randomized study comparing the efficacy of two alpha 1-antagonists, bunazosin retard and prazosin retard, in 185 patients with mild to moderate essential hypertension. Additionally, specific orthostatic tolerance was evaluated by a standardized test (Schellong test). Both 1 to 4 mg prazosin daily and 6 or 12 mg bunazosin daily achieved satisfactory blood pressure reduction (diastolic pressure reduced by at least 10 mm Hg) in 48% and 41% of patients, respectively. The average diastolic blood pressure reduction measured 24 h after drug administration was 9.8 mm Hg in the bunazosin group and 7 mm Hg in the prazosin group. A comparison of blood pressure profiles during specific orthostatic tolerance tests did not show any significant difference between the two groups. However, the symptoms of orthostatic hypotension were significantly less frequent and less severe with bunazosin compared with prazosin. Nineteen patients with essential hypertention were randomized for treatment with either prazosin retard (4 mg) or bunazosin retard (12 mg). The blood flow and the venous capacity were recorded by means of a plethysmograph while the patient was in a supine position and after tilting into the upright position. The peripheral resistance of the calf while the patient was in a supine position during placebo is 38.8 +/- 25.9 U, during bunazosin 28.5 +/- 17 U, and during prazosin 29.7 +/- 27.1 U. The difference between the two alpha-blockers and placebo is statistically significant. There was no effect on venous tone and venous capacity when tilting into the upright position.