naloxone ( 1 mg/kg i.v . ) did not block or reverse the antitussive effects of ( - ) - and ( + ) -codeine but completely antagonized the effects of an ed84 of ( - ) - , ( + ) -morphine , ( - ) - , ( + ) -methadone , levomethorphan and dextromethorphan .
C0009214
codeine
C0026549
morphine