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Vasodilator and inotropic effects of the antiarrhythmic drug melperone
Abstract:
We investigated the hemodynamic and inotropic effects of the new class III antiarrhythmic drug melperone. In eight pentobarbital-anesthetized dogs, the effects of intravenous melperone 0.5, 2.5, and 12.5 mg/kg-1 were tested. During atrial pacing we measured cardiac output (CO), mean aortic blood pressure (MAP), right (RV) and left (LV) ventricular pressures, and LV dP/dt. In six RV papillary muscles isolated from cats and suspended in a muscle bath containing Krebs-Henseleit solution, we studied the direct effects of melperone 10(8)-5 X 10(-5) M. Administration of melperone decreased total peripheral resistance, MAP, RV and LV systolic and end-diastolic pressures, while CO remained unchanged. Melperone increased LV dP/dtmax. The contractile force (F) and dF/dtmax of the isolated ventricular muscle preparations increased slightly with increasing concentrations of melperone, up to 10(-5) M. In conclusion, melperone has vasodilator and slight positive inotropic effects in addition to its class III antiarrhythmic effect.
Insights
Melperone, a new antiarrhythmic drug, acts as a vasodilator and has a slight positive inotropic effect. These findings suggest melperone may offer additional benefits beyond its primary antiarrhythmic action.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
Background:
- Class III antiarrhythmic drugs are crucial for managing cardiac arrhythmias.
- Understanding the full spectrum of a drug's effects, including hemodynamic and inotropic actions, is essential for clinical application.
Purpose of the Study:
- To investigate the hemodynamic and inotropic effects of the novel class III antiarrhythmic drug, melperone.
- To determine melperone's impact on cardiac output, blood pressure, and myocardial contractility.
Main Methods:
- In vivo studies in pentobarbital-anesthetized dogs measuring cardiac output, mean aortic blood pressure, and ventricular pressures during intravenous melperone administration.
- In vitro studies using isolated cat right ventricular papillary muscles to assess direct effects on contractile force and its rate of change.
Main Results:
- Melperone administration resulted in decreased total peripheral resistance, mean aortic blood pressure, and ventricular pressures.
- Cardiac output remained unchanged, while left ventricular dP/dtmax (a measure of contractility) increased.
- Isolated papillary muscle studies showed a slight positive inotropic effect with increasing melperone concentrations.
Conclusions:
- Melperone exhibits vasodilator properties, contributing to decreased blood pressure and peripheral resistance.
- The drug demonstrates a slight positive inotropic effect, enhancing myocardial contractility.
- These findings indicate that melperone possesses vasodilator and positive inotropic effects in addition to its class III antiarrhythmic activity.