title: Prolonged-release oxycodone enhances the effects of existing gabapentin therapy in painful diabetic neuropathy patients.
abstract: BACKGROUND
  Neuropathic pain remains one of the most challenging pain syndromes; under-diagnosed, poorly managed and associated with significant co-morbidity. With standard therapeutic treatments, responders rarely exceed 50% pain relief and the majority suffer from residual pain. Titration to optimum dose is often limited by dose-related adverse events.
  
  
  OBJECTIVE
  This randomized, double-blind, placebo-controlled study assessed the potential benefit of adding oxycodone (OxyContin tablets) to gabapentin. The primary endpoint was to evaluate the analgesic efficacy of co-administration of gabapentin and prolonged-release oxycodone, whilst also evaluating the use of escape medication, sleep quality and global assessment of pain.
  
  
  METHODS
  Three hundred and thirty eight patients with moderate to severe painful diabetic neuropathy despite receiving their maximum tolerated dose of gabapentin, had oral prolonged-release oxycodone or placebo tablets added to their therapy for up to 12 weeks.
  
  
  RESULTS
  Oxycodone-gabapentin reduced pain score by 33% from baseline to end of treatment. The overall treatment effect was greater with oxycodone-gabapentin than with placebo-gabapentin (P = 0.007). Oxycodone-gabapentin also significantly improved pain relief vs gabapentin alone (P = 0.003). Oxycodone-gabapentin co-administration was associated with less escape medication use (P = 0.03) and fewer nights of disturbed sleep (P < 0.05). Discontinuations due to lack of therapeutic effect were much lower (14% vs 54%) with oxycodone-gabapentin. The commonly seen opiate-induced adverse events were not exacerbated by the combination of oxycodone and gabapentin.
  
  
  CONCLUSIONS
  This study provides the first evidence that co-administration of prolonged-release oxycodone and existing gabapentin therapy has a clinically meaningful effect in painful diabetic neuropathy.
authors.affiliation: Pain Clinical Research Hub, King's College Hospital, Denmark Hill Campus, Bessemer Road, London SE5 9PJ, UK. magdi.hanna@kcl.ac.uk
authors.forename: Magdi
authors.initials: M
authors.lastname: Hanna
authors.forename: Cathy
authors.initials: C
authors.lastname: O'Brien
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Wilson
mesh_terms: D000368:Aged; D000588:Amines / Q000008:administration & dosage* / Q000009:adverse effects; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000009:adverse effects; D002121:Calcium Channel Blockers / Q000008:administration & dosage* / Q000009:adverse effects; D003509:Cyclohexanecarboxylic Acids / Q000008:administration & dosage* / Q000009:adverse effects; D003692:Delayed-Action Preparations; D003929:Diabetic Neuropathies / Q000150:complications / Q000188:drug therapy*; D004357:Drug Synergism; D005260:Female; D000077206:Gabapentin; D006801:Humans; D008297:Male; D008875:Middle Aged; D010098:Oxycodone / Q000008:administration & dosage* / Q000009:adverse effects; D010147:Pain Measurement; D017060:Patient Satisfaction; D012893:Sleep Wake Disorders / Q000209:etiology; D016896:Treatment Outcome; D005680:gamma-Aminobutyric Acid / Q000008:administration & dosage* / Q000009:adverse effects
chemical_list: D000588:Amines; D000701:Analgesics, Opioid; D002121:Calcium Channel Blockers; D003509:Cyclohexanecarboxylic Acids; D003692:Delayed-Action Preparations; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin; D010098:Oxycodone