Dr. Mark Ware of McGill University reported in the Journal of the Canadian Medical Association reported results (small study, 23 patients) that demonstrated reduced chronic neuropathic pain for those with damaged nerves. These patients suffered from pain caused by injuries to the nervous system from post-traumatic (e.g. traffic accidents) or post-surgical (e.g. cut nerves) events. Their pain has not been controllable via standard therapies. Four different potencies of cannabis (2.5%, 6%, and 9.4% of tetrahydrocannabinol- the active ingredient in cannabis, as well as a placebo – 0% active ingredient) were among the study parameters.
The subjects were provided a 25 mg dose (via pipe), thrice daily for five days, followed by 9 days off . (This comprised the two-week cycle); a total of four two-week cycles comprised the study (8 weeks). The 25 mg dose was chosen from reported data that 0.4 mg/kg can be inhaled in a single lungful from a pipe (that works out to be 25 mg for 70 kg person). The higher doses clearly reduced pain, as well as reduced anxiety and depression. (Better sleep was also observed). It should be noted that there were more adverse reactions at the higher dosages, but this was a small study.
The next step is to determine whether drug administration via an inhaler is a better administration route compared to this oral (smoking) modality.
This contrasts with an earlier study reported by Dr. Mark Wallace (UC San Diego) in Anesthesiology (another small study of 15 volunteers) which showed that too high a dose may be detrimental. The doses employed for this study were 2%, 4%, and 8% tetrahydrocannabinol by weight. This test then injected capsaicin under the skin (the active ingredient in chili peppers) after five (5) and 45 minutes. No improvement was found at the five-minute injection, but there was relief for the 45 minute capsaicin administration. However, those subjected to the higher dose (8%) felt the pain was worse and not better.
It is possible that the drug may act differently for healthy volunteers, as opposed to those with cancer or multiple sclerosis (where the drug is currently used), or with those with chronic neuropathic pain described above. Another interesting discrepancy is Dr. Ware’s study reported the highest peaks in plasma concentrations occurred between 1 and 4 minutes post drug-administration, with all doses virtually back to zero at 45 minutes (which means one would expect to reduction in pain, as found in Dr. Wallace’s study).