Oxycodone and neuropathic pain
Neuropathic pain is a condition that is usually associated with diabetes.Opioid drugs, plus oxycodone, are mostly used to treat neuropathic pain. All opioids have been studied together as per most reviews. In this review, special consideration is made on oxycodone, at any dose, and by any route of administration; to determine its analgesic efficacy and adverse events for chronic neuropathic pain in adults.
For the original review, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and EMBASE from inception to 6 November 2013 was explored and for this updated version, from January 2013 to 21 December 2015. Reference lists of retrieved studies and reviews, and two online clinical trial registries were also searched. The research in this update has inculcated studies using oxycodone with naloxone, and oxycodone used as add-on treatment to stable, but inadequate, treatment with another class of drug making it different from earlier review.
A study was done to compare any dose or formulation of oxycodone with placebo or another active treatment in chronic neuropathic pain. Examination of study quality and potential bias related problems was done by two authors independently, extracted efficacy and adverse event data. Using standard techniques, they used dichotomous data to calculate risk ratio and numbers needed to treat for one additional event where pooled analysis was feasible. The 'Summary of findings' table was formed by assessing the evidence using GRADE (Grading of Recommendations Assessment, Development and Evaluation).
Five studies delineating on 687 participants; 637 had painful diabetic neuropathy and 50 had postherpetic neuralgia was included. One study used an active placebo (benztropine), but all studies used a placebo comparator. Modified-release oxycodone (oxycodone MR) was titrated to effect and tolerability. Fixed dose combination was used. There was a similar result in the study adding oxycodone MR to stable, ongoing gabapentin, but adding oxycodone MR plus naloxone to stable, ongoing pregabalin did not show any additional effect.
The outcomes equivalent to 'moderate benefit' (at least 30% pain relief or who were much or very much improved), which was experienced by 44% of participants with oxycodone and 27% with placebo (number needed to treat for one additional beneficial outcome (NNT) 5.7) was outlined in three studies (537 participants) of painful diabetic neuropathy. Towards treatment finale, all studies described group mean pain scores. With oxycodone MR alone than with placebo, three studies disclosed a greater pain intensity reduction and better patient satisfaction. There was a comparable result in the study adding oxycodone MR to stable, ongoing gabapentin, but adding oxycodone MR plus naloxone to stable, ongoing pregabalin did not show any additional consequence. More participants witnessed adverse events with oxycodone MR alone (86%) than with placebo (63%); the number needed to treat for an additional harmful outcome (NNH) was 4.3.
No significant differences were observed between groups related to serious adverse events (oxycodone 3.4%, placebo 7.0%) and adverse event withdrawals (oxycodone 11%, placebo 6.4%). Withdrawals due to inadequate efficacy were less frequent with oxycodone MR (1.1%) than placebo (11%), with a number needed to treat to prevent one withdrawal of 10. Similar results were revealed in the add-on studies.
There was only very low quality evidence that oxycodone is good for painful diabetic neuropathy or postherpetic neuralgia treatment. No evidence was obtained for other neuropathic pain conditions. Although, the adverse events typical of opioids emerged to be common.