[General pharmacological actions of traxanox sodium. II. Effects on the cardiovascular system]

The effects of traxanox, an anti-allergic drug, on the cardiovascular system were studied in both anesthetized dogs and cats and in isolated heart preparations from guinea-pigs. In anesthetized dogs, a very small dose of traxanox (0.01 mg/kg, i.v.) had no effect, but 0.1--30 mg/kg caused an increase in respiratory rate, hypotension, bradycardia, a transient decrease followed by an increase in renal blood flow, and a decrease in femoral blood flow. These effects were abolished by vagal block, indicating they are mediated via vagal afferents. In contrast, oral administration of traxanox (100 mg/kg) had no effect on the blood pressure or heart rate of anesthetized dogs. In anesthetized cats, traxanox (3 and 30 mg/kg, i.v.) caused a slight increase in blood pressure, but showed no effect on respiratory rate and heart rate. Both traxanox and theophylline (10(-4)M) caused increases in the beat rate of the atria and the contractile force of the papillary muscle in isolated preparations from guinea-pigs, and they potentiated the positive chronotropic and inotropic responses induced by isoproterenol. On the other hand, in anesthetized and vagotomized dogs, traxanox (3 and 10 mg/kg, i.v.) affected neither the left ventricular contractile force nor the hypotension and positive inotropic and chronotropic responses produced by isoproterenol. Administration of theophylline alone (3 and 10 mg/kg, i.v.) caused hypotension and increases in contractile force and heart rate, but it did not enhance the responses produced by isoproterenol. At doses of 1 and 10 mg/kg (i.v.), traxanox had little effect on either pressor or chronotropic responses to norepinephrine, epinephrine, DMPP and stellate cardiac nerve stimulation. The same doses of traxanox slightly reduced the depressor and chronotropic responses to isoproterenol, acetylcholine and vagus nerve stimulation. These findings suggest that traxanox had no effect on the cardiovascular systems of the animals studied in the dose range (1--5 mg/kg, p.o.) showing anti-allergic activity.