Risk of serotoninergic syndrome w/ MAOIs, SSRIs, triptans. Increased sedative effect by alcohol. Decreased plasma conc by carbamazepine & other enzyme inducers. Decreased analgesic effect w/ opioid agonists-antagonists (buprenorphine, nalbuphine, pentazocine). Increased risk of resp & central depression w/ other opioid derivatives (ie, antitussive drugs & substitutive treatments), benzodiazepines & barbiturates, other anxiolytics, hypnotics, sedative antidepressants & antihistamines, neuroleptics, centrally-acting antihypertensives, thalidomide & baclofen. Increased INR w/ warfarin-like compd. Inhibited metabolism by CYP3A4 inhibitors eg, ketoconazole & erythromycin. Increased risk of convulsion w/ bupropion, serotonin re-uptake inhibitor antidepressants, TCAs & neuroleptics.