Effect of doxapram on respiratory and circulatory systems of dogs

In anesthetized dogs, a single injection (i.v.) of doxapram (0.1 ?? 3 mg/kg) caused a transient rise of systemic blood pressure and increased the rate and volume of respiration, followed by an increase in PaO2 and decrease in PaCO2. When doxapram was infused at a constant rate (0.05 and 0.2mg/kg/min), the same phenomena were observed. These effects of doxapram were compared with those of dimorpholamine anddimefline. The rise of systemic blood pressure induced by doxapram was inhibited by adrenergic blocking agents, ganglionic blocking agents and reserpinization. The same phenomenon induced by doxapram was observed to decrease in spinal dogs. On the other hand, it was potentiated by cocaine. In the heart lung preparation, perfusion pressure, apex contractility, right atrial pressure, cardiac output and heart rate were unaffected by doxapram in any dose applied. Injection of doxapram into the femoral artery increased the femoral blood flow, indicating a decrease in peripheral vessel resistance.