The cardiac and peripheral vascular effects of bretylium tosylate (adrenergic blocking and antiarrhythmic agent) administered intravenously in doses of 5 to 10 mg/kg were evaluated in seven patients with recent myocardial infarction, three with and four without left ventricular failure (LVF). In order to clarify the effects of the drug in vivo, the effect of bretylium on isolated cat papillary muscle was also studied.
The hemodynamic and peripheral vascular effects in all patients were initial transient tachycardia, hypertension and late sustained bradycardia, hypotension with decreased vascular resistance, and increased calf blood flow and venous capacitance, but without any change in cardiac output or filling pressure. In cat papillary muscle, catecholamine-release mediated positive inotropism was evident. Hence, while bretylium may have some beneficial effects in patients with LVF, it should be used with caution if hypotension exists.