Migraine and chronic pain are common disorders and can result in considerable disability.¹ According to the World Health Organization, migraine is ranked 19^th with respect to health disorders causing life lived with disability. The lifetime prevalence of migraine in Canada has been estimated to be 24% in women and 9% in men. Chronic pain is defined as pain that persists for greater than three months.² Chronic pain is associated with a variety of disorders such as chronic low back pain, chronic complex regional pain syndrome (CPRS), fibromyalgia and neuropathy. Estimates of the prevalence of chronic pain in Canada vary between 16% and 40%.³ The variability may be due to differences in the definitions used for chronic pain, sample populations surveyed, and the survey methodologies.³

Treatment for migraine can be divided into two broad categories: acute treatment for migraine attacks and prophylactic treatment to reduce the frequency of migraine attacks.^3,4 Treatment of any type of pain is complex and the best options for treatment still remain unresolved. Increasingly, opioids are being used for the alleviation of pain.⁵ However, long term use of opioids can lead to addiction, development of tolerance, and resistance of chronic pain to opioid analgesia. In addition, it is associated with side-effects such as chronic constipation, dizziness, consciousness disorders, and cognitive impairment.⁵ Hence other modalities for managing pain are needed. Magnesium plays an important physiological role and affects a number of processes. It is the fourth most abundant cation in the body,⁶ and is involved in regulation of protein synthesis, energy production, cell growth, and RNA and DNA synthesis.⁶ Magnesium modulates ion transport by pumps, carriers and channels and can impact signal transduction.⁶ Magnesium acts as a N-methyl-D-aspartate (NMDA) receptor antagonist and blocks the NMDA receptor, resulting in its analgesic effect.^5,6 Activation of the NMDA receptor plays a role in central sensitization and is associated with spontaneous pain and increased reaction to peripheral stimuli.^6,7 As magnesium appears to have an analgesic effect there is growing interest in investigating whether magnesium can be used as an alternative or as an adjunct to opioids for controlling pain.

The purpose of this report is to review the clinical effectiveness of magnesium as an analgesic for the treatment of adult patients with migraine or chronic pain. Additionally, this report aims to review evidence-based guidelines regarding the use of magnesium as an analgesic for the treatment of adult patients with migraine or chronic pain.

Contents

• Context and Policy Issues
• Research Question
• Key Findings
• Methods
  • Literature Search Methods
  • Selection Criteria and Methods
  • Exclusion Criteria
  • Critical Appraisal of Individual Studies
• Summary of Evidence
  • Quantity of Research Available
  • Summary of Study Characteristics
  • Summary of Critical Appraisal
  • Summary of Findings
  • Limitations
• Conclusions and Implications for Decision or Policy Making
• References
• Abbreviations
• Appendix 1. Selection of Included Studies
• Appendix 2. Characteristics of Included Publications
• Appendix 3. Critical Appraisal of Included Publications
• Appendix 4. Main Study Findings and Author’s Conclusions

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