Central and peripheral haemodynamic effects of prenalterol in patients with coronary heart disease.

The acute haemodynamic effects of prenalterol, a selective adrenergic beta-I-receptor agonist were studied in eight patients with coronary heart disease. Prenalterol was administered intravenously in four increasing doses to a cumulative dose of 5.6 mg. Fifteen minutes after the last dose of prenalterol two doses of the selective adrenergic beta-I-receptor antagonist metoprolol were administered intravenously to a cumulative dose of 17-5 mg. Ten minutes after each dose cardiac output, heart rate, arterial blood pressure, pulmonary artery pressure, systolic time intervals and forearm blood flow were determined. Haemodynamic effects of prenalterol: cardiac index and heart rate increased maximally by 38% and 39% respectively. Stroke index was increased by 6-9% after the first and second dose. Mean blood pressure was increased by 9.8 mmHg. Total peripheral resistance index was reduced by 19%. The mean pulmonary artery pressure decreased by 3.8 mmHg and pulmonary resistance index was reduced by 48%. Systolic time intervals were all reduced significantly after the second dose, which reflected the positive inotropic effects of prenalterol. Forearm blood flow increased by 29% and forearm vascular resistance was decreased by 20%. Haemodynamic effects of metoprolol: the haemodynamic changes induced by prenalterol were stepwise counteracted by metoprolol. After the second dose all the haemodynamic variables had returned to the control levels. It is concluded that prenalterol possesses a considerable positive inotropic as well as positive chronotropic effect on the myocardium. Both the chronotropic and inotropic effect of prenalterol was counteracted by metoprolol.

Renal effects of propranolol, practolol and butoxamine in pentobarbital-anesthetized rats.

The renal effects of the beta-adrenergic blockers, propranolol, practolol and butoxamine, were examined in pentobarbital-anesthetized rats. All the beta-blockers, infused i.v., increased urine volume (V), urinary sodium excretion (UNaV) and p-aminohippuric acid clearance without change in inulin clearance. Indomethacin, an inhibitor of prostaglandin biosynthesis, did not affect the renal effects of these beta-blockers. Phentolamine abolished the renal effects of practolol, but not those of propranolol and butoxamine. Haloperidol abolished the renal effects of propranolol and butoxamine, but not those of practolol. A high correlation was found between the increased UNaV and the increased urinary phosphate excretion by butoxamine but not by propranolol and practolol. Therefore, it is suggested that alpha-adrenergic stimulation is involved in the mechanism of diuresis by practolol, a beta1-blocker, and that dopaminergic stimulation is involved in the diuresis caused by butoxamine, a beta2-blocker. Propranolol is similar to butoxamine, and partially similar to practolol.

[The influence of propranolol, practolol and theophylline on the plasma renin activity (author's transl)]. / Beeinflussung der Plasmareninaktivität durch Propranolol, Practolol und Theophyllin

The stimulating effect of theophylline on the plasma renin activity (PRA) under beta-receptor blockade by propranolol or practolol was investigated in 27 patients with essential hypertension of degree I-II. After propranolol and also practolol PRA decreased about thirty per cent of the basal value, increased however by the factor of 2 to 3 after application of theophylline, in spite of the blockade of the beta-receptors indicated by a slight decrease of systolic blood pressure and heart rate. The effect of propranolol and practolol on the basal PRA was not different. Our results show the possibility, to stimulate renin secretion despite blockade of beta receptors by propranolol or practolol, respectively.

Antagonism of fenoterol against beta-blocking drugs bunitrolol and practolol in asthmatics.

In 4 X 10 young white male histamine-sensitive asthmatics without bronchitis or emphysema, the antagonism of fenoterol (40 mug) to bunitrolol (2.5 and 5 mg) or practolol (20 and 30 mg) was tested in an open comparative trial. Pulse frequency and several physiological parameters were determined before and after histamine challenge test, after injection of beta-blocking drug and after injection of fenotrolol. All groups were found to be equally sensitive to histamine. Bunitrolol and practolol were found to have no influence on histamine effect. It was also found that bunitrolol in the dosages tested is a much more potent beta-blocking drug in the bronchi compared to practolol in the dosages tested were equivalent. beta-Blockade of practolol (20 or 30 mg) could completely be antagonized by 40 mug fenoterol; this dosage was not sufficient to antagonize 2.5 or 5 mg bunitrolol.