Effects of tibalosine, a new α‐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 bpm) 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 E 2 , F 2α , and F α metabolites. During tibalosine treatment, creatinine clearance decreased by 20 mllmin and serum creatinine rose by 0.04 mg/100 ml. The increase in serum sodium by 0.05 mmolll 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 × 10 6 cells/mm 3 ) 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. Clinical Pharmacology and Therapeutics (1983) 33, 556–564; doi: 10.1038/clpt.1983.76