Smoking pot can make some of the pain go away, without the patient getting high.
The finding comes from what researchers in Montreal believe to be the first outpatient clinical trial of smoked cannabis, involving 21 people with chronic neuropathic pain.
The results, which included improvements in mood and sleep, were published Monday in the Canadian Medical Association Journal.
Dr. Mark Ware and colleagues at McGill University and McGill University Health Centre got the ball rolling for the study almost a decade ago, but found it was a long road to get all the necessary approvals and import a convincing marijuana placebo from the United States.
But they plowed ahead, supported by a grant from the Canadian Institute for Health Research, because they felt it was important to generate some scientific data.
Marijuana is illegal in Canada but can be used medicinally in some circumstances. In 2001, Health Canada brought in marijuana medical access regulations outlining conditions for possessing, producing and using the herb for medical purposes.
Despite the years that have passed, “the debate rages on about medical marijuana,” Ware said.
“We hear this a lot from policy makers and from regulatory colleges, especially here in Canada … there is very little evidence, and many of them aren’t aware of any evidence that smoked cannabis has any medical value.”
Marijuana with potencies of 2.5 per cent, six per cent and 9.4 per cent of the active ingredient THC were obtained from Prairie Plant Systems, the company that was given a government contract 10 years ago to produce a safe, standardized supply of marijuana.
A placebo came from the U.S., where an alcohol extraction process was used to remove the active ingredient, and the herb was reconstituted so it looked like a green leafy material, Ware said.
There was a lot of paperwork and back-and-forth.
“Importing cannabis from the United States is not a trivial issue in this environment,” Ware noted.
Patients were given a special pipe bought on the Internet and 25-milligram capsules of a substance to put in the pipe and light. The smoke was to be inhaled once — three times a day for five days — and patients didn’t know whether they were getting a placebo or one of three different potencies of active drug.
Participants used each strength of marijuana product for five days, separated by nine days of washout without cannabis.
“They would inhale that in a slow, smooth, single inhalation, hold their breath for 10 seconds,” then exhale slowly, Ware said.
The first dose was in the hospital, under observation.
“Even with this kind of fixed dosing and limited exposure, we were able to show in a blinded fashion that the patients did obtain some analgesia, improvements in sleep quality and on one of the subscales of the quality-of-life measure, we found that the anxiety was mildly improved as well,” Ware said.
“This may help in developing policy, or improving policy, or improving doctors’ willingness to consider this as an approach when all else has failed.”
Side-effects — the euphoria associated with smoking pot — were “very, very rare,” Ware said.
“I think because the doses we used were very low,” he explained.
“The plasma levels which we found, and which are reported in the trial, show levels of THC in the blood of around … 40 to 50 nanograms per millilitre in the plasma. And we know that recreational users hit blood levels of around 100 and 150 nanograms per millilitre.”
Prairie Plant Systems now offers medical marijuana that is 12 per cent THC, Ware observed.
“So would we get better results if we had slightly higher THC levels, would we get better results if the patients could use it for longer periods, or if they could use it more frequently during the day?” he asked. “I think these are questions that we can’t answer.”
Prof. Henry McQuay, who works at a pain relief unit in Oxford, U.K., wrote a commentary in the journal, saying that the researchers should be congratulated for tackling the project given that the regulatory hurdles “must have been a nightmare.”
“The big picture here is a political one in a way, where Canada has decided to legalize medicinal use of cannabis in this arena, but many other countries have not,” he said in an interview.
“It’s another brick in that wall, that says here’s evidence that some people do indeed show some pain-relieving benefit from smoking cannabis.”
Dr. Igor Grant, director of the Center for Medicinal Cannabis Research at the University of California in San Diego, said the finding is consistent with data reported from his centre, “and basically shows that there is a beneficial effect of smoked cannabis on neuropathic pain.”
“The potencies we have typically used have been around four per cent and as high as seven per cent, so that (9.4 per cent) is a higher potency than we’re experienced with,” he said.
“But in reading the article, it seems like the patients tolerated it reasonably well.”
Neuropathic pain is a bit different than the pain of a broken leg, for instance, and is a more chronic, burning, unpleasant sensation, he explained.
“Many patients don’t respond completely to existing treatments, and so it’s useful to have another agent … available, and I think there’s good evidence now cannabis may represent one of those additional agents.”
The researchers say more studies are needed using higher potencies of marijuana, longer duration and flexible dosing to see if pain levels can be reduced even further.
Grant remarked that smoke inhalation raises several issues, and his centre is completing two studies on pain using a vaporization form of cannabis.
“People who are non-smokers may have difficulty tolerating it (smoke),” he said. “Secondly, there’s the issue of second-hand smoke, which people may not like.”
There are also the side-effects of smoking, and practical issues, such as concerns about lighting up in a hospital where there are oxygen tanks, he added.
– Article from The Toronto Star.