HYDROCODONE IS A CENTRALLY-ACTING SEMISYNTHETIC NARCOTIC ANTITUSSIVE AND ANALGESIC WITH MULTIPLE ACTIONS QUALITATIVELY SIMILAR TO THOSE OF CODEINE. THE PRECISE MECHANISM OF ACTION OF HYDROCODONE AND OTHER OPIATES IS NOT KNOWN; HOWEVER, HYDROCODONE IS BELIEVED TO ACT DIRECTLY ON THE COUGH CENTER. IN EXCESSIVE DOSES, HYDROCODONE, LIKE OTHER OPIUM DERIVATIVES, WILL DEPRESS RESPIRATION. THE EFFECTS OF HYDROCODONE IN THERAPEUTIC DOSES ON THE CARDIOVASCULAR SYSTEM ARE INSIGNIFICANT. HYDROCODONE CAN PRODUCE MIOSIS, EUPHORIA, AND PHYSICAL AND PSYCHOLOGICAL DEPENDENCE.