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Patients with central neuropathic pain associated with multiple sclerosis (MS) should have better prospects of pain relief now that a randomised controlled trial in Denmark has shown that an oral synthetic derivative of cannabis is effective. This is a hopeful sign for those whose pain does not respond to current drugs.
The randomised double blind, placebo controlled crossover trial in 24 patients with MS and central pain established that dronabinol up to 10 mg daily for three weeks reduced pain intensity significantly by the end of treatment compared with placebo. The estimated relative difference in pain reduction from baseline between dronabinol and placebo was −20.5% (95% confidence interval −37.5 to −4.5). Median pain relief score was significantly raised for dronabinol (3 (0–6.7)) versus placebo (0 (0–2.3)) too, and mental health was better but functional ability was unchanged. Side effects were widespread, affecting the CNS and including musculoskeletal problems, though these were mostly tolerable once dosage was lowered. The patients were aged 23–55 and had had MS and pain for a median of seven and 4.5 years, respectively.
Cannabis derivatives seem to reduce allodynia or hyperalgesia in neuropathic pain and central pain in animals, and they might be helpful for pain suffered by up to 80% of MS patients. However, until now it was not known whether they would be effective specifically against central pain reported in about a third of MS patients.