Moguisteine: a novel peripheral non-narcotic antitussive drug

1. The antitussive effects of moguisteine have been compared with codeine in several experimental models of cough in guinea-pigs and dogs. 2. Moguisteine and codeine dose-dependently (respective ED50 values are given in parentheses) inhibited cough induced in guinea-pigs by 7.5% citric acid aerosol (25.2 and 29.2 mg kg-1, p.o.), by 30 microM capsaicin aerosol (19.3 and 15.2 mg kg-1, p.o.), by mechanical stimulation (22.9 and 26.4 mg kg-1, p.o.) and by tracheal electrical stimulation (12.5 and 13.9 mg kg-1, p.o.). 3. Moguisteine was effective against cough induced by tracheal electrical stimulation in dogs (ED50 17.2 mg kg-1, p.o.); codeine was not tested because of its emetic effect. 4. After repeated dosing (12-15 days), moguisteine did not induce tolerance in either guinea-pigs or dogs. 5. Moguisteine did not interact with opiate receptors, since it did not show affinity for [3H]-naloxone binding sites and furthermore naloxone (5 mg kg-1, s.c.) did not antagonize its antitussive effects. 6. Moguisteine had no antitussive effect after i.c.v. administration (20 micrograms), whilst codeine (2-10 micrograms) and dextromethorphan (2.5-20 micrograms) were highly effective. 7. Our findings demonstrate that moguisteine is a novel peripherally acting non-narcotic antitussive agent, the mode of action of which remains to be elucidated fully.