The Pharmaceutical Journal Vol 263 No 7072 p811
November 20, 1999 Clinical

Phase I cannabis trial completed

A phase I trial using cannabis has been completed, according to GW Pharmaceuticals, the company licensed by the UK Home Office to develop cannabis-based prescription drugs. The study used six healthy volunteers who were given formulations of cannabis containing different ratios of the cannabinoids tetrahydrocannabinol and cannabidiol. Three formulations were used: sublingual drops, a sublingual spray and a nebulised inhalation. These formulations were used because they gave rapid absorption and the effects of the drug could be felt within 15 minutes. Eventually, this would allow patients to titrate the dose that they needed at a given time and so provide rapid relief of acute symptoms. Dr Geoffrey Guy (chairman, GW Pharmaceuticals) said at a press briefing on November 16 that a range of formulations would probably be made available in the future to provide patients with both relief of symptoms and longer-lasting maintenance treatment. He added that the full results of the trial would be published next year.

Dr Guy inspecting cannabis plants that will be used in future trials (GW Pharmaceuticals)

Once the results of the Phase I trial had been fully analysed, and subject to Medicines Control Agency approval, Phase II trials could begin. Patients who would be recruited would be multiple sclerosis sufferers, patients with spinal cord injury and patients with phantom-limb pain. Phase III trials would take the form of a number of "n=1" trials. Individuals would have a "run-in" period and would then be given three active preparations and placebo, each for one to two weeks and in a random order. Treatment would then be repeated but in a different order. If the patient showed a positive response, they would be put into a longer safety trial. It was expected that between 200 and 300 patients might be recruited next year. Dr Guy said that these trials should be complete by 2002. It was hoped that some of the trial subjects would be current users of illicit cannabis, as participation in the trial would provide them with a legal, quality assured supply.
During the current trial, side effects had not been serious and were generally transient. Dr Guy said that the correct dose for each individual should provide therapeutic effects without the patient "needing to get high". GW Pharmaceuticals was hoping to increase the therapeutic index of its preparations by adjusting the ratios of cannabinoids that they contained.
The aim of the development programme is to prepare data for product licence approval. "Subject to the necessary regulatory approvals, we hope to have a cannabis-based medicine available for prescription by doctors within three to four years", said Dr Guy.