Opioid agonist doses for oxycodone and morphine dependence: Findings from a retrospective case series

Introduction: Use of opioid agonist treatments for prescription opioid (PO) dependence is rapidly increasing. Current guidelines are based on research with heroin users. This study aimed to examine methadone and buprenorphine dose requirements for PO-dependent people.

Design and Methods: A retrospective case series of PO-dependent patients entering methadone and buprenorphine treatment. Daily oral morphine equivalent (OME) doses at baseline were calculated using standard dose conversion calculations. Dose conversion tables were used to estimate opioid agonist doses, based on starting dose of PO. Baseline methadone and buprenorphine dose at days 7 and 28 were examined. Linear models were fit to the data.

Results. Participants (n = 44) were 67% male, mean age 41 years (SD 10 years); 69% reported a pain condition. The methadone group (n = 21) had a mean PO dose of 704.5 mg OME (SD 783.5 mg) prior to treatment, and mean methadone dose of 45.3 mg (SD 13.1 mg) at day 7 and 61.6 mg (SD 20.8 mg) at day 28. The buprenorphine group (n = 23) had a mean PO dose of 771.7 mg OME (SD 867.7 mg) prior to treatment, with a mean dose of 14.6 mg (SD 8.3 mg) at day 7 and 18.1 (SD 8.9 mg) at day 28. Linear relationships were not found between OME and opioid agonist dose.

Conclusions: Opioid agonist dosages varied substantially between individuals, and from predicted dosages based on dose conversion tables. Use of conversion tables to guide selection of opioid agonist dosage may compromise patient safety.