POT CAN LOWER CHRONIC PAIN WITHOUT THE HIGH

Study Used Cannabis From Prairie Plant Systems

Briefly inhaling cannabis three times a day eases a kind of chronic
pain that affects tens of thousands of Canadians -- without making
them high -- Montreal researchers are reporting.

The new study, the first clinical trial in the world to allow patients
to take marijuana home with them and "self-dose," found that for
people with neuropathic pain -- a common and dreaded condition that
causes electric, stabbing pain -- smoking cannabis reduced pain,
improved mood and helped them sleep.

Three different potencies (2.5 per cent, six per cent and 9.4 per
cent) of THC, the active ingredient in marijuana, were tested against
a placebo, or "dummy" pot in 21 patients with neuropathic pain, none
of whom had responded to standard treatments.

Participants inhaled a single dose through a pipe three times daily
for five days, followed by a nine-day "washout" period. They were
instructed to inhale for five seconds while the cannabis was lit, hold
the smoke in their lungs for ten seconds and then exhale.

Pain was measured on an 11-point scale ranging from "no pain" to
"worst pain possible."

Patients reported less pain, better sleep and less anxiety when they
were smoking the highest concentration of THC, compared with the placebo.

It wasn't a massive reduction in pain: The average daily pain
intensity was 5.4 with 9.4 per cent THC, versus 6.1 with the placebo.

"But the patients that we were recruiting had to be patients that had
tried and failed all other conventional treatments," said lead author
Dr. Mark Ware, director of clinical research at the Alan Edwards Pain
Management Unit at the McGill University Health Centre.

Neuropathic pain -- which is caused by damage to nerves -- affects as
much as two per cent of the population. The Montreal study involved
patients with post-trauma or post-surgical pain -- radiating pain from
prolapsed discs, for example, or burning pain from an incision.

"Through no fault of the surgeon's, it's impossible to do an operation
without cutting through some nerves," Ware said. "For some people, for
some reason, even after the tissue has healed they have persistent
pain at the site of the operation.

"All of these were very refractory, very difficult pain problems to
resolve. Any improvement in pain was quite remarkable."

As many as 15 per cent of patients with chronic non-cancer pain and
multiple sclerosis report using marijuana, and Ware said that when he
asked his own pain patients, similar numbers reported using marijuana.
"There clearly was an unmet need."

"We're not going to argue that smoked cannabis is the be-all and
end-all of pain management," Ware said.

"It simply opens the door to the fact that cannabinoids may be an
additional tool in the physician's tool box, along with other
medications and other non-pharmacological approaches."

During the study, "psychoactive effects" were rare: After more than
1,000 different "administrations" of cannabis during the course of the
study, people reported feeling "high" on only three occasions.

Ware said it's possible their plasma levels of THC didn't reach the
levels found with recreational smokers. "Street users have access to
cannabis that can be anywhere from 15 to 20 per cent THC."

An expert in pain relief at Oxford University said the study "adds to
the trickle of evidence" that cannabis may help some patients
struggling with chronic pain. Dr. Henry McQuay lauded the Montreal
team for even taking on the study, "given that the regulatory hurdles
for their trial must have been a nightmare."

Those hurdles included getting through ethics approval; setting up a
ventilated room where patients could use the drug under supervision
for the first dose; finding a safe, legal supply of cannabis that had
well-controlled levels of THC (cannabis was obtained from Prairie
Plant Systems Inc. in Saskatoon) and finding a believable placebo.

Ware ended up importing a THC-extracted cannabis from the U.S.
National Institute of Drug Abuse. It still looked like cannabis. It
just had no THC in it.

"These weren't experienced cannabis users," he said. "They didn't have
a lot of prior expectations to go on."

"When we started the study there was no evidence this was effective,"
said Ware. Three other trials have since been completed, two that were
restricted to neuropathic pain in patients with HIV.

"Now it's clear that smoked cannabis does have analgesic properties,"
Ware said. "The question now is, where do we go with that?"

His team is just concluding another study on the long-term safety
issues.

Some prescription sprays and medications are now available that
contain cannabinoids. Cannabinoids bind to receptors in the brain that
play a role in modulating pain.

The study, which appears in the latest issue of the Canadian Medical
Association Journal, comes as more than 5,000 health professionals
from across Canada and the world gather in Montreal this week for the
13th World Congress on Pain.