Even though the specific system of action of codeine remains not known, it is usually thought to be mediated in the agonism of opioid receptors, notably the mu-opioid receptors.4 Morphine was Earlier postulated to add into the analgesic influence of codeine as a result of O-demethylation of codeine to morphine by CYP2D6. Specifically, CYP2D6 bad me