fentanyl + codeine

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

fentanyl + promethazine

use alternative or monitor respiratory rate, BP, ECG if anesthesia use; decr. fentanyl by at least 25-50%, consider decr. promethazine dose, use lowest effective doses and shortest duration of concomitant tx: combo may incr. risk of profound CNS and respiratory depression, psychomotor impairment, seizures, severe hypotension (including orthostasis, syncope), QT prolongation, cardiac arrhythmiassevere constipation/paralytic ileus, other anticholinergic adverse effects (additive effects)

fentanyl + codeine

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

codeine + codeine

avoid combo: combo may incr. risk of profound CNS and respiratory depression, psychomotor impairment, severe hypotension (including orthostasis, syncope), serotonin syndrome, severe constipation, paralytic ileus, other adverse effects (additive effects, duplicate therapy)

promethazine + codeine

avoid combo if antitussive use; otherwise use alternative or monitor respiratory rate, BP; decr. codeine dose by at least 25-50%, consider decr. promethazine dose, use lowest effective doses and shortest duration of concomitant tx: combo may incr. risk of profound CNS and respiratory depression, psychomotor impairment, seizures, severe hypotension (including orthostasis, syncope), severe constipation/paralytic ileus, other anticholinergic adverse effects (additive effects)