acetaminophen + acetaminophen

limit acetaminophen from all sources to standard max acetaminophen doses: combo may incr. acetaminophen levels, risk of hepatotoxicity, other adverse effects (additive effects, duplicate therapy)

codeine + oxycodone

avoid combo if antitussive use; otherwise use alternative or monitor respiratory rate, BP, serotonin syndrome sx, especially during initiation/titration; decr. oxycodone start dose by at least 50%, consider decr. codeine dose, use lowest effective doses and shortest duration of concomitant tx: combo may incr. risk of profound CNS and respiratory depression, psychomotor impairment, severe hypotension (including orthostasis, syncope), serotonin syndrome, severe constipation/paralytic ileus, other anticholinergic adverse effects (additive effects)