Methadone titration in opioid-resistant cancer pain

AIM: To assess the use of methadone in patients with cancer pain who fail to respond to increasing doses of other opioids or experience intolerable side-effects from them. METHOD: Inpatients of a specialist palliative care unit were titrated onto oral methadone. The dose was calculated as 10% of the previous morphine equivalent dose, up to maximum of 40 mg, given every 3 h as required for analgesia. When daily requirements were stable it was divided into two regular doses. Pain was assessed on a five-point verbal rating score (VRS): a good response was defined as a fall in VRS of two points or more. Results are expressed as median (range). RESULTS: Thirty-three patients (13 men, 20 women, age 61 (34-91) years), 26 with inadequate analgesia and seven with intolerable opioid related side-effects, were converted to methadone from diamorphine (12), morphine (19) or fentanyl (two). Morphine equivalent dose was 480 (20-1200) mg/day prior to titration. Pain was neuropathic (11), nociceptive (three) or mixed (19). Stabilisation on methadone was complete in 3 (2-18) days in 29 (88%) patients at 80 (20-360) mg/day. Twenty-six (78%) had a good response. Four (12%) patients were withdrawn during titration (three entered terminal phase, one failed to respond). During follow-up 15 (45%) required alteration of methadone dose. Twenty-three (70%) patients were discharged home at 12 (4-26) days. In all cases the stable dose of methadone was less than the previous morphine equivalent, and there was a weak correlation between them. CONCLUSIONS: This method of methadone titration often results in improved pain control in patients with morphine resistance or intolerance. It requires careful titration in a specialist inpatient unit as there is no reliable formula for dose equivalence.