Tramadol Metabolism and Clinical Implications

Comparison with Other Opioids

Codeine is a prodrug that must be metabolized to morphine to produce significant analgesic effects, unlike tramadol, according to the European Society for Medical Oncology 1
Codeine has little to no analgesic effect until metabolized to morphine via CYP2D6, making it ineffective in poor metabolizers and potentially toxic in ultrarapid metabolizers, as stated by the European Society for Medical Oncology 2
Dihydrocodeine is metabolized to dihydromorphine (not morphine) via CYP2D6, but this represents only a minor metabolic pathway, as reported by the Association of Anaesthetists 3

Tramadol has approximately one-tenth the potency of morphine, with a recommended maximum daily dose of 400 mg for immediate-release formulations or 300 mg/day for extended-release formulations, according to the National Comprehensive Cancer Network 4
Lower doses are recommended for older adults (≥75 years) and those with hepatic or renal dysfunction to reduce the risk of adverse effects, particularly seizures, as advised by the National Comprehensive Cancer Network 4

Tramadol has distinct side effects related to its dual mechanism of action, including a risk of serotonin syndrome when combined with serotonergic medications, as noted by the American Society of Health-System Pharmacists 5