Science Cannabis

170 THE SCIENCE OF MARIJUANACannabis was commonly used in the nineteenth century to treatepilepsy, but there has been little interest more recently since the antiepilepticdrugs described above became available in the 1930s and subsequently.Animal data do show antiseizure activity of THC in some experiments,but there are also conditions in which cannabinoids can makeanimals more susceptible to seizure activity. An interesting observation isthat the nonpsychoactive cannabinoid cannabidiol also appeared to beactive as an antiseizure compound in some animal studies. There havebeen very few clinical studies with this compound, but one placebocontrolledtrial in 15 treatment-resistant epileptic patients suggested thatcannabidiol in doses of 200 or 300 mg by mouth might have beneficialeffects. Attempts to follow up these potentially useful findings, however,failed to confirm any positive effect of this dose of cannabidiol on seizurefrequency, although a single patient treated with a higher dose of cannabidiol(900-1200 mg per day) seemed to benefit (Hollister, 1986; BritishMedical Association Report, 1997). Cannabidiol has no appreciableactivity at either of the known cannabinoid receptors, so if it is active asan anticonvulsant this must presumably involve an action at some hithertoundiscovered cannabinoid receptor.Anecdotal reports of the use of smoked marijuana by epileptic patientsare mixed. Some patients claim to derive significant benefits andwere able to reduce the doses of conventional antiepileptic drugsneeded. At least one case has been reported, however, in which oralTHC (20 mg) precipitated a seizure in a patient with a previous historyof epilepsy. Other reports suggest that cannabis may counteract the effectivenessof drugs used in the treatment of petit mal epilepsy. Even themost ardent advocates of the medical uses of marijuana caution:Cannabis is by no means a cure-all for epilepsy. . . . Epileptics who areinterested in trying cannabinoids should be careful about oral THC. Thosewho use cannabinoids should be aware that they may become more susceptibleto seizures when they withdraw from treatment.(Rosenthal et al., 1997)It is difficult to see epilepsy as a high priority area for research onthe potential use of cannabis or cannabinoids. The introduction of sev-