Do not misuse cough syrup. Codeine metabolism happens in the liver and is mediated primarily in the first pass by CYP 2D6 (to morphine) and CYP 3A4 (norcodeine). Codeine and morphine can be glucuronidated in a second pass of metabolism, but watch for renal function in hospitalized patients as morphine-6-glucuronide is renally excreted. Because it is pharmacologically active as an analgesic as well, use caution in patients with renal failure. Genetic mutations in 2D6 have been observed and result in different pharmacokinetics for codeine. See references below. This case is 2 cases combined. Both are de-identified. This video is not individual medical advice and are for general educational purposes only. I do not give medical advice over the internet.