Effect on resting blood pressure and blood pressure homeostasis of short-term administration of the alpha 1-adrenergic receptor antagonist, trimazosin, in hypertension

Long-term haemodynamic effects of sustained-release trimazosin at rest and during exercise in essential hypertension

The long-term haemodynamic effect of sustained-release trimazosin (mean daily dose 418 mg) at rest and during exercise has been examined in 14 male patients (age 30-61 y) with previously untreated mild or moderate essential hypertension. Cardiac output (dye dilution), heart rate and intra-arterial blood pressure were measured supine and sitting at rest, and during bicycle exercise. After 11 months of trimazosin treatment the mean casual blood pressure was reduced from 165/106 mmHg to 147/92 mmHg. The intra-arterial systolic and diastolic pressure was reduced by 3-7% at rest and during 50, 100 and 150 W exercise. Total peripheral resistance was reduced by 8-14% and cardiac output was slightly higher (2-8%) in all situations. Stroke volume and heart rate remained unchanged, as did body fluid volumes (isotope dilution) and body weight. Side effects were minor and transient. Thus, the haemodynamic responses to trimazosin are similar to but weaker than those of other alpha 1-adrenoceptor blockers. The efficacy of the sustained-release formulation of trimazosin was low and daily doses above 600 mg are likely to be needed by many patients.