Alexander J. Clark

Pharmacological management of chronic neuropathic pain - Consensus statement and guidelines from the Canadian Pain Society

Neuropathic pain (NeP), generated by disorders of the peripheral and central nervous system, can be particularly severe and disabling. Prevalence estimates indicate that 2% to 3% of the population in the developed world suffer from NeP, which suggests that up to one million Canadians have this disabling condition. Evidence-based guidelines for the pharmacological management of NeP are therefore urgently needed. Randomized, controlled trials, systematic reviews and existing guidelines focusing on the pharmacological management of NeP were evaluated at a consensus meeting. Medications are recommended in the guidelines if their analgesic efficacy was supported by at least one methodologically sound, randomized, controlled trial showing significant benefit relative to placebo or another relevant control group. Recommendations for treatment are based on degree of evidence of analgesic efficacy, safety, ease of use and cost-effectiveness. Analgesic agents recommended for first-line treatments are certain antidepressants (tricyclics) and anticonvulsants (gabapentin and pregabalin). Second-line treatments recommended are serotonin noradrenaline reuptake inhibitors and topical lidocaine. Tramadol and controlled-release opioid analgesics are recommended as third-line treatments for moderate to severe pain. Recommended fourth-line treatments include cannabinoids, methadone and anticonvulsants with lesser evidence of efficacy, such as lamotrigine, topiramate and valproic acid. Treatment must be individualized for each patient based on efficacy, side-effect profile and drug accessibility, including cost. Further studies are required to examine head-to-head comparisons among analgesics, combinations of analgesics, long-term outcomes, and treatment of pediatric and central NeP.

impact on health-related quality of life and costs of managing chronic neuropathic pain in academic pain centres : results from a one-year prospective observational Canadian study

Chronic pain, including neuropathic pain, has a high prevalence and, therefore, its management is an important public health issue. Aggressive management guided by pain specialists can provide adequate pain relief; however, delays in access to these specialists can negatively impact patient’s well-being. The economic value of managing chronic neuropathic pain in academic centres is discussed, in addition to determining the long term outcomes of this type of pain management.

Cannabinoids and pain management

controlled, parallel-group trial studying the analgesic effects of two different doses of nabilone, a synthetic analogue of THC, in managing acute postoperative pain following major surgery. 5 Unfortunately, the study was prematurely terminated after 18 months. The results of this study demonstrated that nabilone administration was not associated with a decrease in morphine consumption in patients following major surgery. In addition, nabilone at high doses significantly increased pain scores at rest and upon movement. The investigator concluded that, although cannabinoids may be effective in relieving chronic pain in humans, their role in the treatment of acute postoperative pain is uncertain, and requires further clinical evaluation. Small sample size, early termination of the study, and the lack of standardization of surgical procedures with possible variation in intensity of postoperative pain (e.g., total hip replacement vs total knee replacement) may limit the conclusions that can be drawn from this study. Previous studies examining cannabinoids in treating postoperative pain have also demonstrated only a modest analgesic effect. 6 A systematic review concluded that cannabinoids are no more effective than codeine in controlling acute pain, although this was a conclusion based upon only one Phase II study. 7 While the current study suggests a very limited role for cannabinoids in postoperative pain, it is important to recognize that this may change as novel, more potent and more specific synthetic cannabinoid analogs, with limited central nervous system effects, are developed. The role of cannabinoids in managing chronic pain is more promising. A systematic review of studies available prior to 2002 identified seven randomized controlled trials examining cannabinoids in chronic pain. These studies demonstrated that oral THC preparations exhibit a moderate analgesic effect, equivalent