Pain management strategies for patients on methadone maintenance therapy: a systematic review of the literature

Context: Prescription opioid and heroin abuse has increased substantially in recent years. Enrolment on opioid agonist therapy programmes is consequently increasing as well. As a result of these trends, more patients who present with acute pain secondary to a malignancy are also on chronic methadone maintenance therapy (MMT) for substance abuse. This combination of diagnoses presents a pain management challenge for palliative care providers.

Objectives: This paper aims to gather and review the available medical literature pertaining to the use of opioid analgesia in methadone-maintained patients.

Methods: The authors searched PubMED, PsychINFO, EMBASE, Clinical Key, the Cochrane Library and CINAHL from their inception to May 2015 for relevant articles. All articles that discuss opioid therapy in adult patients on methadone maintenance for opioid addiction with cancer or advanced illness were included. Data were extracted and study quality was rated independently by the authors.

Results: Our searches resulted in 680 hits. Of those, only 7 met inclusion criteria for the study. Most of the studies favoured the use of methadone either in scheduled divided doses every 4-8 hours or by continuous intravenous infusion. The overall strength of the evidence was poor, consisting mainly of case series, case reports and 1 single-centre retrospective cohort study lacking a comparison group.

Conclusions: Treating MMT-maintained patients with methadone for analgesia may be preferable to using other opioid analgesics. However, there are many systems barriers that may make this approach challenging and the evidence favouring methadone over other opioid analgesics is weak.