Inotropic and haemodynamic effects of d- and d,l-sotalol: comparison with other antiarrhythmics.

The inotropic effects of sotalol in comparison to other antiarrhythmic drugs were tested in an experimental model allowing isovolumic measurements independently of the loading conditions. All class I drugs had a similar negative inotropic effect. d,l-Sotalol caused a dose-dependent depressant effect on the rate of left ventricular pressure development. The same held true for l-sotalol. In contrast, d-sotalol, in clinical doses, revealed no significant inotropic effects in normal hearts. In a postischemic model, d-sotalol led to a further deterioration of left ventricular function. It could be demonstrated by autonomic blockade that this effect was mainly the result of the remaining weak beta-blocking activity of the d-isomer in addition to its class III action. After intravenous administration of amiodarone in doses of 10 mg.kg-1, no significant inotropic effects were found in normal rats.