Antitussive effect of captopril, an angiotensin converting enzyme inhibitor, in the rat

The effects of acute treatment with captopril, an angiotensin converting enzyme inhibitor, on the capsaicin-induced cough reflex were examined in rats. Intraperitoneal injection of captopril in doses of 3 and 10 mg/kg decreased the number of coughs dose-dependently. Although the peak effect was similar to that of morphine (0.5 mg/kg), the duration of captopril's effect (10 mg/kg) was longer than that of morphine. Furthermore, while pretreatment with naloxone significantly decreased the duration of the antitussive effect of captopril, it had no significant effect on the early-phase (within 60 min) effect of captopril. These results suggest that the mechanism which underlies the antitussive effect of captopril involves mediation by both nonopioid and opioid systems.