IACM-Bulletin of December 23, 2007

Science — THC reduces chronic pain in patients who do not get sufficient pain relief from opioids

According to a study conducted by researches of Harvard Medical School in Boston THC (dronabinol) was able to reduce pain in 30 patients taking opioids for chronic pain. Phase I of this 2-phase study was a double-blinded trial in which subjects were administered once on three occasions either 10 mg or 20 mg of THC or identical placebo capsules. Phase II was an open-label individually dosed trial of THC as add-on medication to patients on stable doses of opioids.

Results of the Phase I study showed that patients who received THC experienced decreased pain intensity compared with placebo. No differences in benefit were found between the two THC doses. In the Phase II trial, titrated THC contributed to significant relief of pain and increased satisfaction compared with baseline. The incidence of side effects was dose-related. Overall, the use of THC was found to result in additional analgesia among patients taking opioids for chronic non-cancer pain.

(Source: Narang S, Gibson D, Wasan AD, Ross EL, Michna E, Nedeljkovic SS, Jamison RN. Efficacy of Dronabinol as an Adjuvant Treatment for Chronic Pain Patients on Opioid Therapy. J Pain 2007 Dec 12 [Electronic publication ahead of print])

UK — Medicines regulatory agency publishes an information report on Sativex

On 13 December the Medicines and Healthcare products Regulatory Agency (MHRA) published a Public Information Report on Sativex, a cannabis extract of the British company GW Pharmaceuticals approved for medical use in Canada. The MHRA has taken this unprecedented step due to its view of the “huge public interest” in Sativex and the fact that approximately 1200 patients in the UK have so far received the medicine on prescription on a named patient basis.

The report concludes that the safety profile of Sativex is considered acceptable in principle for the proposed patient population and indication, providing sufficient efficacy is demonstrated. GW Pharmaceuticals is currently conducting a clinical study to clarify the remaining questions on efficacy of their extract. The report includes a consensus statement by a panel of independent experts. They concluded: "We conclude that Sativex meets a currently unmet medical need in patients where there is no other conservative treatment option. It is our view that Sativex should be licensed and become available on prescription for patients with spasticity due to multiple sclerosis, and we urge the MHRA to do so."

The report is available on the website of the MHRA: http://www.mhra.gov.uk/home/idcplg?IdcService=GET_FILE&dID=38433&noSaveAs=0&Rendition=WEB

(Sources: Press release by GW Pharmaceuticals of 13 December 2007, MHRA Report on Sativex of 13 December 2007)

Science — Qualitative similar composition of cannabis and tobacco smoke

Canadian researches investigated the chemical composition of cannabis and tobacco smoke. Smoking of cannabis and tobacco cigarettes, which weighed about 800 mg was carried out on smoking machines. The results showed qualitative similarities with some quantitative differences. With a normal tobacco smoke rhythm, the smoke of both tobacco and cannabis cigarettes contained an average of about 40 mg tar. Following a more intense inhalation to simulate usual cannabis smoking the amount of tar by cigarette increased to 80-100 mg. Thus, the amount of inhaled noxious substances is less dependent from the smoked material than from the smoking pattern. The results are agreement with previous research.

With the same smoking pattern, ammonia was found in cannabis smoke at levels of about 20-fold greater than that found in tobacco, which according to the authors may have been due to higher nitrate levels in cannabis due to fertilization. Hydrogen cyanide was about 2.5 times, nitric oxide (NO) about 4 times and some aromatic amines were found in cannabis smoke at concentrations 3-5 times those found in tobacco smoke. Tobacco-specific nitrosamines were not found in cannabis smoke. Concentrations of mercury, cadmium, lead and arsenic as well as low-molecular weight carbonyl compounds (formaldehyde, acetaldehyde, etc.) were found at considerably lower concentrations in cannabis smoke compared to tobacco smoke. Cannabis smoke also contained somewhat less amounts of polycyclic aromatic hydrocarbons.

The study is available at:

http://pubs.acs.org/cgi-bin/sample.cgi/crtoec/asap/pdf/tx700275p.pdf

(Source: Moir D, Rickert WS, Levasseur G, Larose Y, Maertens R, White P, Desjardins S. A Comparison of Mainstream and Sidestream Marijuana and Tobacco Cigarette Smoke Produced under Two Machine Smoking Conditions. Chem Res Toxicol. 2007 Dec 7 [Electronic publication ahead of print])

News in brief

Science — Cancer of the large intestine

It is well-known that THC and other cannabinoids reduce survival of cancer cells in the large intestine. In a letter to the International Journal of Cancer, British researchers warned that the long-term use of cannabinoid receptor antagonists might increase the risk of cancer of the large intestine. The cannabinoid receptor antagonist rimonabant is in use in Europe against obesity. The risk for the development of this cancer is already increased in obesity and this risk may be further increased by rimonabant. (Source: Wright KL, et al. Int J Cancer. 2007 Dec 12 [Electronic publication ahead of print])