A new study suggests that cannabis derivatives do not improve severe symptoms of spasticity in multiple sclerosis (MS).
The researchers who conducted the study say no definite conclusions about efficacy can be drawn because of the small number of patients who took part (Neurology 2002;58:1404). However, they add that the study is the largest randomised controlled trial on this topic to have been conducted so far.
Joep Killestein, VU Medical Centre, Amsterdam, and colleagues gave 16 patients capsules of placebo, cannabis plant-extract, or synthetic tetrahydro-cannabinol (THC), each for four weeks, in a double-blind, crossover study.
The researchers report that both the svnthetic THC and the plant-extract were generally well tolerated by the patients, who had progressive MS with severe spasticity. However, side effects such as dizziness and headache were more common with plant extract treatment than with placebo. One patient experienced acute psychosis lasting for five hours when the dose of plant-extract was increased. In addition, five patients reported increased spasticity during plant-extract treatment.
Patients’ muscle tone did not improve significantly when they were given active treatments and ratings of overall disability declined. “The results do not suggest therapeutic benefit of either THC or plant-extract treatment,” conclude the researchers.
However, the researchers say that the route of administration and dose of the preparations used could explain the lack of efficacy. They say: “THC is absorbed reasonably well from the gut, but the process is slow, with a large range between and within individuals.” For the first two weeks of active treatment, patients received two daily doses of 2.5mg THC or plant-extract, containing the same level of THC. If this was well tolerated, the dose was increased to 5mg twice daily. The researchers comment that higher dosing regimens are not supported because of the risk of adverse drug events.
In an accompanying editorial, Professor Alan Thompson and Dr David Baker, both of the Institute of Neurology, University College London, note that a study of 660 patients receiving plant-extract, THC and placebo is underway in the United Kingdom. “Fundamental questions about the potential value of cannabis remain unanswered and hopefully will be adequately addressed in the current UK trial,” they say.
