Interaction between proxyphylline and salbutamol.

Salbutamol increased significantly the bronchodilating effect of proxyphylline both in experimental animals and in asthmatic patients. In guinea pigs (modified Konzett-Rössler method) the reduction in response to metacholine caused by increasing doses of proxyphylline and salbutamol significantly exceeded that of either drug alone. In a double-blind, randomized cross-over study conducted on 3 consecutive days, asthmatic patients received 500 mg proxyphylline orally three times daily. On the 2nd or 3rd day a significantly greater improvement in the peak expiratory flow was found after the combination of proxyphylline and salbutamol (3 mg p.o.) in comparison with proxyphylline and placebo. Salbutamol had no significant effect on the plasma concentrations of proxyphylline, which varied between 14 and 22 microgram/ml. The combination of oral proxyphylline and salbutamol is clinically useful in increasing drug response without increased adverse effects.