<p>Increased risk of serotonin syndrome with other drugs that enhance monoaminergic neurotransmission (e.g. TCAs, triptans, SSRIs, serotonin and norepinephrine reuptake inhibitors). Enhanced sedative effect with benzodiazepines, barbiturates, antipsychotics, H1-antihistamines and other opioids. Increased potential for addiction with mixed &mu;-opioid agonists/antagonists (e.g. nalbuphine, pentazocine) or partial &mu;-opioid agonists (e.g. buprenorphine). Increased systemic exposure with strong inhibitors of UGT1A6, UGT1A9 and UGT2B7 isoenzymes. Decreased efficacy with strong enzyme inducers (e.g. rifampicin, phenobarbital).</p>