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Biomedical subjects

L Brorson

Publications and source records attributed to L Brorson.

27 records · Page 2Linked to original sources
PubMed1975

Minoxidil--haemodynamic and clinical experiences with a new peripheral vasodilator.

Minoxidil, a new peripheral vasodilator, given orally to hypertensive men in single doses of 5-25 mg, produced no haemodynamic changes within one hour after administration. After repeated oral doses within 24 hours to a total of 15-45 mg and after 10 mg t.i.d. orally for one week, moderate decreases in BP were seen concomitant with tendencies to increased heart rate and cardiac output. Clinically, oral minoxidil 10-50 mg daily in combination with diuretics and adrenergic beta-receptor blocking agents achieved an improved BP control in five patients with sustained arterial hypertension and unsatisfactory response to previous treatment. However, in four of the five patients minoxidil had to be withdrawn because of side-effects. It is concluded that minoxidil, producing a hypotensive effect of slow onset, may find a place as a therapeutic addition to symptomatic patients with severe and therapy-resistant hypertensive cardiovascular disease, provided adequate measures are taken to counteract side-effects, especially water retention and development of oedemas.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Effects of concentration and steric configuration of propranolol on AV conduction and ventricular repolarization in the dog.

To investigate the electrophysiological effects of propranolol in vivo over a wide range of plasma concentrations and to distinguish effects due to beta-blockade from those due to a direct membrane action, His bundle electrograms were recorded, and ventricular effective refractory periods (VERP) and monophasic action potential duration (MAP) were measured in anesthetized control dogs and in dogs given three graded infusions of d- or dl-propranolol. Dogs were excluded if the plasma concentrations attained did not fall in predefined ranges of 25--125, 125--700, and 700--3,000 ng/ml. Isoproterenol sensitivity tests were performed to determine the relative beta-blocking potency of the isomers at the three concentration ranges. The highest concentration of d-propranolol had approximately the same beta-blocking potency as the lowest concentration of dl-propranolol. Mean AH and HV intervals in the His bundle electrogram increased with the concentration of dl-propranolol, and the increase was greater than with d-propranolol (p less than 0.03) at the first and second concentration steps but not significantly different at the highest concentrations of d- and dl-propranolol. VERP and MAP increased directly with concentration of d- and dl-propranolol. Although the mean increases of VERP and MAP tended to be greater in the dl-propranolol group, the differences between d- and dl-propranolol were not statistically significant at any concentration. We conclude that prolongations of atrioventricular and His-Purkinje conduction are stereospecific responses and are due to beta-blockade. The specific mechanism for the prolongation of ventricular repolarization and refractoriness are effects of propranolol that could not be definitively classified in this study.

Action Potentials↗
PubMedDate not supplied

Effect of the tetracyclic antidepressant drug maprotiline on cardiac electrophysiology in human volunteers.

The tetracyclic antidepressant drug maprotiline was given intravenously to seven healthy volunteers in order to evaluate its effect on sinus node automaticity, on the atrioventricular conduction system judged from Hisbundle electrograms, and on the repolarization of the right atrium and ventricle judged from the refractoriness and monophasic action potential duration. Sinus recovery time decreased after the drug, probably as a result of the anticholinergic action of maprotiline. No other significant changes were obtained. The electrophysiological effects of maprotiline on the atrium, AV-nodal conduction, and the ventricle seem less pronounced than those of tricyclic antidepressant drugs and this may explain the less pronounced arrhythmogenic effect of maprotiline.

Action Potentials↗