Research

SMOKED CANNABIS FOR CHRONIC NEUROPATHIC PAIN: A RANDOMIZED CONTROLLED TRIAL

Background: Chronic neuropathic pain affects 1%-2% of the adult
population and is often refractory to standard pharmacologic
treatment. Patients with chronic pain have reported using smoked
cannabis to relieve pain, improve sleep and improve mood.

Methods: Adults with post-traumatic or postsurgical neuropathic pain
were randomly assigned to receive cannabis at four potencies (0%,
2.5%, 6% and 9.4% tetrahydrocannabinol) over four 14-day periods in a
crossover trial. Participants inhaled a single 25-mg dose through a
pipe three times daily for the first five days in each cycle,
followed by a nine-day washout period. Daily average pain intensity
was measured using an 11-point numeric rating scale. We recorded
effects on mood, sleep and quality of life, as well as adverse events.

Results: We recruited 23 participants (mean age 45.4 [standard
deviation 12.3] years, 12 women [52%]), of whom 21 completed the
trial. The average daily pain intensity, measured on the 11-point
numeric rating scale, was lower on the prespecified primary contrast
of 9.4% v. 0% tetrahydrocannabinol (5.4 v. 6.1, respectively;
difference = 0.7, 95% confidence interval [CI] 0.02-1.4).
Preparations with intermediate potency yielded intermediate but
nonsignificant degrees of relief. Participants receiving 9.4%
tetrahydrocannabinol reported improved ability to fall asleep
(easier, p = 0.001; faster, p ( 0.001; more drowsy, p = 0.003) and
improved quality of sleep (less wakefulness, p = 0.01) relative to 0%
tetrahydrocannabinol. We found no differences in mood or quality of
life. The most common drug-related adverse events during the period
when participants received 9.4% tetrahydrocannabinol were headache,
dry eyes, burning sensation in areas of neuropathic pain, dizziness,
numbness and cough.

Conclusion: A single inhalation of 25 mg of 9.4% tetrahydrocannabinol
herbal cannabis three times daily for five days reduced the intensity
of pain, improved sleep and was well tolerated. Further long-term
safety and efficacy studies are indicated. (International Standard
Randomised Controlled Trial Register no. ISRCTN68314063)

Related Articles

Highlights Can. Med. Assoc. J. 2010 182: 1489. [Full Text]
http://www.cmaj.ca/cgi/content/full/182/14/1489

More evidence cannabis can help in neuropathic pain Henry J. McQuay
Can. Med. Assoc. J. 2010 182: 1494-1495. [Full Text]
http://www.cmaj.ca/cgi/content/full/182/14/1494