Pain intolerance in opioid-maintained former opiate addicts: effect of long-acting maintenance agent

Patients on methadone maintenance therapy are relatively intolerant of pain, a finding hypothesized to reflect a hyperalgesic state induced by chronic opioid administration. To explore if the intrinsic activity of the opioid maintenance agent might affect expression of hyperalgesia in this population, withdrawal latency for cold-pressor (CP) pain was compared between small groups of methadone-maintained (n = 18), buprenorphine-maintained (n = 18), and matched control (n = 18) subjects. The opioid-maintained groups had equal and significantly shorter withdrawal latencies than controls, however it is possible that high rates of continued illicit opioid use precluded finding differences between methadone and buprenorphine groups. Differential effects of maintenance agent were found for the few subjects without illicit opioid use, such that withdrawal latencies for methadone-maintained (n = 5) were less than for buprenorphine-maintained (n = 7) which were less than controls (n = 18). Diminished pain tolerance in patients receiving opioid maintenance treatment has significant clinical implications. More research is needed to determine if buprenorphine offers advantages over methadone in this regard.