Do cannabinoids possess anti-convulsant properties?
(Press agency article):
An Ontario judge ruled on Wednesday that a Toronto man could grow and use marijuana to control his severe epilepsy, saying the law banning the medicinal use of the drug was unconstitutional. The landmark ruling was a major victory for advocates of the legalization of marijuana for medical use and for defendant Terrence Parker, 42, who has fought for 20 years to use the drug to control his severe form of epilepsy. (…)
The Epilepsy Association of Toronto welcomed the ruling, saying: "We feel people should have opportunities and options to choose from. People who have epilepsy, by in large, are on medication to try and control their seizures. Lots of them do not get control of their seizures through those medicines and are searching for another way."
Source: Reuters of 10 December 1997.
(Gordan and Devinsky):
Animal and human research on the effects of marijuana on seizure activity are inconclusive. There are currently insufficient data to determine whether occasional or chronic marijuana use influences seizure frequency. Some evidence suggests that marijuana and its active cannabinoids have antiepileptic effects, but these may be specific to partial or tonic-clonic seizures. In some animal models, marijuana or its constituents can lower the seizure threshold and thus facilitate seizures. Preliminary, uncontrolled clinical studies suggest that cannabidiol may have antiepileptic effects in humans. (...) Marijuana use or withdrawal could potentially trigger seizures in susceptible patients.
Modified according to: Gordon E, Devinsky O. Alcohol and marijuana: effects on epilepsy and use by patients with epilepsy. Epilepsia 2001 Oct;42(10):1266-72.
(Carlini and Cunha):
Fifteen patients suffering from secondary generalized epilepsy refractory to known antiepileptic drugs received either 200 to 300 mg cannabidiol daily or placebo for as long as 4.5 months. Seven out of the eight epileptics receiving cannabidiol had improvement of their disease state, whereas only one placebo patient improved.
Source: Carlini EA, Cunha JM. Hypnotic and antiepileptic effects of cannabidiol. J Clin Pharmacol 1981;21(8-9 Suppl):417S-427S.
(U.S. Institute of Medicine):
There are anecdotal and individual case reports that marijuana controls seizures in epileptics, but there is no solid evidence to support this belief. While there are no studies indicating that either marijuana or THC worsen seizures, there is no scientific basis to justify such studies. (...)
The potential anti-epileptic activity of cannabidiol (CBD) has been investigated, but is not promising. Three controlled trials were conducted in which cannabidiol was given orally to patients with generalized grand mal seizures or focal seizures. Two of these studies were never published. (...)
Even if CBD had anti-epileptic properties, these studies were likely too small to demonstrate efficacy. Proving efficacy of anticonvulstants generally requires large numbers of patients followed for months because the frequency of seizures are highly variable and the response to therapy varies depending on seizure type.
Source: Joy JE, Watson SJ, Benson JA, eds. Marijuana and Medicine: Assessing the Science Base. Washington DC: Institute of Medicine, National Academy Press, 1999.