title: Pharmacogenetics of chronic pain management.
abstract: OBJECTIVE
  The experience of chronic pain is one of the commonest reasons individuals seek medical attention, making the management of chronic pain a major issue in clinical practice. Drug metabolism and responses are affected by many factors, with genetic variations offering only a partial explanation of an individual's response. There is a paucity of evidence for the benefits of pharmacogenetic testing in the context of pain management.
  
  
  METHODS
  We reviewed the literature between 2000 and 2013, and references cited therein, using various keywords related to pain management, pharmacology and pharmacogenetics.
  
  
  RESULTS
  Opioids continue to be the mainstay of chronic pain management. Several non-opioid based therapies, such as treatment with cannabinoids, gene therapy and epigenetic-based approaches are now available for these patients. Adjuvant therapies with antidepressants, benzodiazepines or anticonvulsants can also be useful in managing pain. Currently, laboratory monitoring of pain management patients, if performed, is largely through urine drug measurements.
  
  
  CONCLUSIONS
  Drug half-life calculations can be used as functional markers of the cumulative effect of pharmacogenetics and drug-drug interactions. Assessment of half-life and therapeutic effects may be more useful than genetic testing in preventing adverse drug reactions to pain medications, while ensuring effective analgesia. Definitive, mass spectrometry-based methods, capable of measuring parent drug and metabolite levels, are the most useful assays for this purpose. Urine drug measurements do not necessarily correlate with serum drug concentrations or therapeutic effects. Therefore, they are limited in their use in monitoring efficacy and toxicity.
authors.affiliation: Department of Clinical Pathology, Sunnybrook Health Sciences Center, Toronto, Canada; Division of Clinical Pharmacology and Toxicology, The Hospital for Sick Children University of Toronto, Canada; Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Canada. Electronic address: b.kapur@utoronto.ca.
authors.forename: Bhushan M
authors.initials: BM
authors.lastname: Kapur
authors.affiliation: Division of Clinical Pharmacology and Toxicology, The Hospital for Sick Children University of Toronto, Canada.
authors.forename: Prateek K
authors.initials: PK
authors.lastname: Lala
authors.affiliation: Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Canada.
authors.forename: Julie L V
authors.initials: JL
authors.lastname: Shaw
mesh_terms: D000277:Adjuvants, Pharmaceutic / Q000627:therapeutic use*; D000701:Analgesics, Opioid / Q000627:therapeutic use*; D059350:Chronic Pain / Q000188:drug therapy* / Q000235:genetics*; D004347:Drug Interactions / Q000235:genetics; D006801:Humans; D059408:Pain Management / Q000379:methods; D010597:Pharmacogenetics / Q000379:methods
chemical_list: D000277:Adjuvants, Pharmaceutic; D000701:Analgesics, Opioid
keywords: Chronic pain; NSAIDs; Opioids; Pain management; Pharmacogenetics; Pharmacokinetics; Triptans