Cardiovascular effects of the positive inotropic agents pimobendan and sulmazole in vivo.

The effects of the cardiotonics sulmazole (AR-L 115 BS, Vardax) and pimobendan (UD-CG 115 BS) on cardiac contractility, heart rate and diastolic blood pressure were investigated in vivo in pithed guinea pigs, anaesthesized cats and conscious dogs. UD-CG 115 BS proved to be about 5-6 times more active than AR-L 115 BS as a positive inotropic agent in pithed guinea pigs and anaesthetized cats. The hypotensive effects of AR-L 115 BS and UD-CG 115 BS were comparable in pithed guinea pigs whereas UD-CG 115 BS showed stronger hypotensive effects than AR-L 115 BS in anaesthetized cats. A dose of 5 mg/kg of AR-L 115 BS evoked positive inotropic effects during 4-5 h after oral administration to conscious dogs. UD-CG 115 BS (1 mg/kg p.o.) induced a strong increase in LV-dp/dtmax in conscious dogs. These positive inotropic effects lasted for more than 8 h with negligible effects on diastolic blood pressure and heart rate.