Respiratory depression in a patient receiving oral methadone for cancer pain

Methadone is a synthetic opioid with excellent oral bioavailability, variable, but long duration of action and extremely low cost. Our group has found that methadone is well tolerated in patients with difficult pain syndromes who are receiving high dose opioids. However, because of high interpersonal variation in bioavailability and the long duration of action of this drug, treatments should be highly personalized. We report on a 61 year old cancer patient who was switched from 84 mg/day of subcutaneous hydromorphone to 90 mg/day of oral methadone. On this dose, she developed respiratory depression and non-cardiogenic pulmonary edema that responded to subcutaneous naloxone and methadone discontinuation. Our findings suggest that standard equlanalgesic tables are unreliable for methadone titration. Switchovers should take place slowly and in a personalized fashion.