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Objective To establish the efficacy of medications, incidence of adverse events (AEs), and withdrawal rates associated with the pharmacological management of chronic spinal cord injury pain. Methodology PubMed, MEDLINE, Embase, CINAHL, Web of Science, CENTRAL, and PsycINFO were searched (November 2017) and updated (January 2020). Two independent review authors screened and identified papers for inclusion. Results Twenty-one studies met inclusion requirements for efficacy analysis and 17 for AE and withdrawal rate analysis; no additional papers were included from the updated 2020 search. Treatments were divided into six categories: anticonvulsants (n = 6), antidepressants (n = 3), analgesics (n = 8), anti-spasticity medications (n = 2), cannabinoids (n = 1), and other (n = 2). Trials of anticonvulsants, antidepressants, and cannabinoids included long-term follow-up trials (2 weeks to 4 months), and trials of analgesics and anti-spasticity medications, among others, were short-term trials (0–2 days). Effectiveness for neuropathic pain was found for pregabalin (3/3 studies) and lidocaine (2/3 studies). Studies using ketamine also reported effectiveness (2/2), but the quality of these papers was rated as poor. The most frequently reported AEs included dizziness, dry mouth, nausea, and constipation. Pregabalin was associated with a higher risk of somnolence (risk ratio [RR] 3.15, 95% confidence interval [CI]: 2.00–4.98) and dizziness (RR 2.9, 95% CI: 1.58–5.30). Ketamine was associated with a higher risk of reduced vision (RR 9.00, 95% CI: 0.05–146.11), dizziness (RR 8.33, 95% CI: 1.73–40.10), and somnolence (RR 7.00, 95% CI: 1.73–40.1). Withdrawal rates ranged from 18.4% for antidepressants to 0–30% for anticonvulsants, 0–10% for anti-spasticity medications, 0–48% for analgesics, 28.6% for cannabinoids, and 0–22.2% for other medications. Conclusion Pregabalin was found to be effective for neuropathic pain vs placebo. Cannabinoids were ineffective for neuropathic pain. AEs are a common cause for withdrawal. The nature of AEs was poorly reported, and AE reporting should be improved in future randomized controlled trials. [ABSTRACT FROM AUTHOR]

Objective. Opioids are one of the most commonly prescribed medicines for chronic pain. However, their use for chronic pain has been controversial. The objective of this literature review was to identify the role of genetic polymorphisms on patient treatment parameters (opioid dose requirements, response, and adverse effects) for opioids used in malignant and nonmalignant chronic pain. The opioids that this review focuses on are codeine, morphine, oxycodone, tramadol, and fentanyl. Method. A literature search of databases Medline and Embase was carried out, and studies up to April 2016 were included in this review. Studies were included based on a combination of key words: chronic pain and related terms, pharmacogenetics and related terms, and opioids and related terms. Results. Among the 1,408 individual papers retrieved from the search in Medline and Embase, 32 original articles were included in this review, with none related to codeine. The 32 papers reported various study designs, opioids, and polymorphisms being studied for associations with treatment outcomes. This literature review reveals that variants in ABCB1, OPRM1, and COMT have been replicated for opioid dosing and variants in ABCB1 have been replicated for both treatment response and adverse effects. Conclusions. Currently, there are few validated studies to form a strong evidence base to support pharmacogenomics testing when initiating opioid therapy. However, the field of pharmacogenomics in chronic pain is likely to expand over the coming years, with the increasing number of treatment options available and larger cohorts being assembled in order to identify true associations. [ABSTRACT FROM AUTHOR]