Effects of tibalosine, a new alpha-adrenoceptor antagonist, in essential hypertension.

Tibalosine is a phenylethylamine derivative known to lower arterial pressure in hypertensive animal models. In a double-blind cross-over study, 12 patients with essential hypertension, on a constant sodium intake, received placebo and tibalosine, 150 mg daily. Standing (-5.5/-6.0 mm Hg) and supine (-8.5/-7.5 mm Hg) blood pressure and standing (-7.0 bmp) and supine (-7.5 bpm) pulse rate were reduced by tibalosine. Plasma renin activity (-0.41 ng/ml/hr) and plasma angiotensin 1 (-47 pg/ml) and angiotensin II (-3.0 pg/ml) levels decreased. There were no significant changes observed in plasma aldosterone or in the urinary excretion of aldosterone, kallikrein, or prostaglandin E2, F2 alpha, and F alpha metabolites. During tibalosine treatment, creatinine clearance decreased by 20 ml/min and serum creatinine rose by 0.04 mg/100 ml. The increase in serum sodium by 0.05 mmol/l was not accompanied by significant changes in body weight. There were small, but significant reductions in hemoglobin (-0.4 gm/100 ml), hematocrit (-1.5%), and erythrocyte count (-0.15 X 10(6) cells/mm3) during tibalosine intake, while blood glucose rose by 4.0 mg/100 ml. Apart from a slight tranquilizing effect in two anxious patients, no obvious sedation was observed. Subjective complaints were as frequent during placebo as during active treatment periods.