IACM-Bulletin of February 20, 2005

Science — Cannabis effective in cancer pain

According to a press release by GW Pharmaceuticals a cannabis extract containing equal amounts of THC and CBD (Sativex) was effective against cancer pain in a Phase III clinical trial. A THC rich extract was not superior to placebo.

The double-blind study included 177 patients with severe cancer pain that was not responding adequately to strong opioid medication (e.g. morphine). One third received Sativex, one third the THC rich extract and one third placebo. The drugs were administered by means of a spray into the mouth. In addition to study medication, all patients remained on their existing analgesic medication.

Sativex achieved a statistically significant improvement in comparison to placebo in pain (p=0.014). Approximately 40% of patients on Sativex showed a greater than 30% improvement in their pain. The other active arm of this study, GW’s THC extract did not show a significant effect in pain (p=0.24). This trial therefore suggests that Sativex is the more effective product for use in cancer pain. The data on the side effects showed the medicines to be generally well tolerated.

“We will now be actively reviewing the next steps, including a possible further Phase III confirmatory clinical trial, towards securing regulatory approvals for the use of Sativex in cancer pain,” said Dr. Stephen Wright, GW's Research & Development Director.

(Source: Press release of GW Pharmaceuticals of 19 January 2005, www.gwpharm.com)

Science — Heavy cannabis use may negatively influence blood flow in the brain

The use of cannabis can affect blood flow in the brain. According to a study by researchers of the US National Institute on Drug Abuse these effects may last longer than one month in heavy users. Authors write in the journal Neurology, that "these findings might provide a partial explanation for the cognitive deficits observed in a similar group of marijuana users."

They monitored the blood flow through the brains of 54 marijuana smokers, among whom the light users smoked an average of 11 joints per week, the moderate users 44 joints and the heavy users 131 joints per week on average. People who smoked cannabis had higher blood flow through their brains than non-users. There was also greater resistance to the blood flow.

After one month without cannabis the investigation was repeated. The resistance to blood flow of light and moderate users was starting to return to normal, while it was still elevated in heavy users.

Research of recent years has demonstrated that cognitive deficits in cannabis users get normal after some days and weeks of abstinence but that normalization after very heavy use may need longer than one month. In the new study the heaviest user smoked 50 joints per day.

(Sources: New Scientist of 7 February 2005; Herning RI, et al. Cerebrovascular perfusion in marijuana users during a month of monitored abstinence. Neurology 2005;64(3):488-93.)

News in brief

USA — ID cards in California

California health officials plan to issue identification cards to medical marijuana users that would prohibit state and local authorities from seizing their stashes or prosecuting them, officials said on 15 February. The cards will be available this summer for patients in at least 10 counties, and state-wide by the end of the year, said state Department of Health Services spokeswoman Norma Arceo. Five other states - Alaska, Hawaii, Nevada, Oregon and Washington - have similar ID cards. (Source: San Francisco Chronicle of 16 February 2005)

Belgium — Cannabis law changed

In October 2004 the Belgium Court of Justice nullified the drug law of 2003, which legalised the possession of cannabis for private use by adults, because its wording was too imprecise. Now the government adapted the law. The new text says that people over 18 may possess 3 grams of marijuana or one plant for personal use. Cases of inconvenience (distribution, selling, dealing, using under 18, using in jail, near schools, in public places, in company of under-aged) are not tolerated. The law was put into practice on 1 February. (Source: Directive of the Ministry of Justice of 31 January 2005)

Holland — Medicinal cannabis

The Office of Medicinal Cannabis (OMC) introduced a new medicinal cannabis variety for sales to pharmacies on 14 February 2005. The new variety (Cannabis flos, variety Bedrobinol) is produced by Bedrocan and replaces the recently withdrawn variety SIMM 18. It has almost exactly the same strength (approx. 18 per cent dronabinol and approx 0.2 per cent cannabidiol). (Source: Press release of the OMC of 11 February 2005)

Science — CB2 receptors and pain

US researchers investigated the mechanisms by which the activation of the peripheral cannabinoid-2 receptor decreases pain. Their study suggests that CB2 receptor activation stimulates release of beta-endorphin, an endogenous opioid, which acts at local opioid receptors to inhibit pain perception. (Source: Ibrahim MM, et al. Proc Natl Acad Sci U S A 2005 Feb 10; [Electronic publication ahead of print])

Science — Cannabidiol and tumours

In cell experiments cannabidiol (CBD), a non-psychotropic cannabinoid, inhibited the migration of tumour cells. CBD caused a concentration-dependent inhibition of the migration of glioma cells. Gliomas are malignant brain tumours. These anti-tumour properties of CBD were independent of cannabinoid receptors. (Source: Vaccani A, et al. Br J Pharmacol 2005 Feb 07; [Electronic publication ahead of print])