Effect of a sustained-release formulation of trimazosin in mild to moderate hypertension

A single-blind study was conducted to evaluate the blood pressure (BP) reduction and side effects of a sustained-release (SR) formulation of trimazosin in patients with mild to moderate hypertension. Eighteen individuals (age, 21-65 yr; mean diastolic BP, greater than 95 mm Hg) with essential hypertension were enrolled into the study. Each patient's dose was titrated to a range of 150-900 mg/d, with polythiazide added as necessary to achieve BP control. Four hours following the maximum titrated dose of trimazosin, mean standing and supine diastolic BPs were significantly lower than baseline readings. Supine systolic BP and supine and standing heart rate were not significantly lower than baseline. At 24 hours after administration of the maximum dose, there were no significant differences in heart rate of BP compared with baseline readings. Five of 16 patients responded to trimazosin therapy alone. Of the 11 treatment failures with trimazosin alone, five were therapeutic failures and six discontinued because of side effects. Only two of these 11 patients achieved satisfactory results with the combination therapy. Trimazosin SR acutely lowers BP three to six hours after administration. It appears to have a duration of action longer than six hours, but it is not sustained for 24 hours. The proportion of patients failing to respond in this sample was very high and suggests that for similar patients, the drug does not appear to be a very useful antihypertensive agent.