| In vivo study | In myocardial infarction and sham-operated rats, Conivaptan(0.03,0.1, and 0.3 mg/kg, I. V.) dose-dependently increased urine output and decreased urine osmolality. In rats with myocardial infarction, Conivaptan(0.3 mg/kg, I. V.) significantly reduced right ventricular systolic pressure, left ventricular end-diastolic pressure, lung/body weight, and right atrial pressure. In rats with myocardial infarction, Conivaptan(0.3 mg/kg, I. V.) significantly increased dP/dt (Max)/left ventricular pressure. Conivaptan produces an acute increase in urine volume (UV) and a decrease in osmolality (UOSM). At the end of the treatment, V(1a)/V(2)-AVP receptor antagonist treated cirrhotic rats did not show hyponatremia or hypotonicity. Conivaptan also restored U(Na)V without affecting creatinine clearance and blood pressure. In dogs, Conivaptan(0.01 to 0.1 mg/kg, I. V.) exerts a dose-dependent diuretic effect without increasing the urinary excretion of electrolytes, inhibited the pressor effect of exogenous vasopressin in a dose-dependent manner (0.003 to 0.1 mg/kg, I. V.) and, at the highest dose (0.1 mg/kg, I. V.), it almost completely blocks the vasoconstriction induced by exogenous vasopressin. Conivaptan(0.1 mg/kg, I. V.) improves cardiac function as evidenced by a significant increase in left ventricular dP/dt Maxima, cardiac output and stroke volume. In dogs with congestive heart failure, Conivaptan (0.1 mg/kg, I. V.) reduced anteroposterior load, as evidenced by a significant decrease in left ventricular end-diastolic pressure and total peripheral vascular resistance. |