Cannabis reduces opioid dose in the treatment of chronic non-cancer pain.

To the Editor: Cannabinoids block pain responses in virtually every laboratory pain model tested. In models of acute or physiological pain, cannabinoids are highly effective against thermal, mechanical, and chemical pain, and are comparable to opioids in potency and efficacy.1 In models of chronic pain, cannabinoids exhibit efficacy in the modulation of both inflammatory2 and neuropathic pain.3 Recent reviews describe an endogenous cannabinoid system involved in pain modulation that produces analgesia through the same brainstem circuitry involved in opioid analgesia.1,4,5,6 Although co-administration of ∆-9-tetrahydrocannabinol (THC) with μ opioid agonists can potentiate the antinociceptive effects of each agent, an opioid is not required for cannabinoid analgesia.5,6 Co-administration of a cannabinoid may lead to a lower opioid requirement. In an Nof-1 trial, oral THC reduced the pain of familial Mediterranean fever such that the use of breakthrough opioid for pain relief decreased significantly.7 Recently, in Canada, the Medical Marijuana Access Program allows patients to apply to Health Canada for access to dried cannabis for medicinal purposes. Although smoked cannabis is not an ideal delivery system, it is efficient and results in plasma concentration curves parallel to those seen after intravenous administration.8 We present three patients who used small doses of smoked marijuana in combination with an opioid.