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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]

Objective This systematic review assesses the effectiveness and side effects of celiac plexus neurolysis ( CPN) in the treatment of upper abdominal cancer pain, and evaluates whether there are any differences between the percutaneous and endoscopic ultrasound-guided ( EUS) denervation techniques. Methods Five databases were searched, expanded by assessing the reference lists of all retrieved papers. Sixty-six publications fulfilled the inclusion/exclusion criteria and were included in the systematic review. Randomized controlled trials were available for the percutaneous CPN, and therefore meta-analyses were performed for pain, opioid consumption, and specific side effects. The quality of life data were too heterogeneous to be assessed by a meta-analysis, and evidence for EUS CPN could only be evaluated by observational studies. Results Meta-analyses show that percutaneous CPN significantly improves pain in patients with upper abdominal cancer, with a decrease in opioid consumption and side effects. It is unclear whether there is any change in quality of life. Case series suggest that EUS CPN improves pain. No conclusion can be made about EUS CPN's influence on opioid consumption. Although CPN is a safe procedure, side effects and complications can occur with both the percutaneous and EUS techniques. Conclusions Following this review, evidence suggests that CPN should be considered in patients with upper abdominal cancer where the pain is not adequately controlled with systemic analgesics or when significant opioid-induced side effects are present. The percutaneous approach remains the standard technique as robust evidence for EUS CPN is lacking. [ABSTRACT FROM AUTHOR]