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Letter to the editor:
In the late nineteenth century cannabis was often prescribed for Parkinsonian tremor, apparently with benefit. Marijuana is known to contain several active substances with multiple properties and these include psychotropic, hypnotic, tranquillising, antiemetic, anticonvulsant and analgesic actions. The most potent constituent is thought to be tetrahydrocannabinol, (THC) and its hedonic properties have long been exploited for recreational purposes.
One of our patients whose severe Parkinsonian tremor was resistant to medications including anticholinergics and beta-blockers claimed that he had obtained dramatic relief after smoking marijuana on three separate occasions, with benefit lasting up to three hours. We attempted to verify this claim by comparing the effects of marijuana with more conventional agents.
Five patients with idiopathic Parkinsonís disease, and severe tremor were studied; all have previously been unresponsive to anticholinergics; levodopa, bromocriptine and beta-blockers had been tried in 4,3 and 2 cases respectively. All patients were given on consecutive days: 1) marijuana smoked as a cigarette, 2) diazepam 5 mg orally, 3) levodopa/carbidopa 250 mg/25 mg orally (Sinemet 275), 4) apomorphine 1.5 mg subcutaneously. All drugs were given in the morning after withdrawal of normal medication overnight, and in the case of the levodopa on the empty stomach. Before administration of apomorphine, patients were given domperidone, a peripheral dopamine antagonist, to prevent side effects of nausea and hypotension. The marijuana was prepared as a cigarette containing approximately 1 g of the shredded leaf (2.9% THC by weight). Patients were assessed for Parkinsonian disability before and at intervals after dosing using a modified Webster scale; particular care was taken in assessing tremor and the patientsí subjective assessment was recorded.
None of the patients, including the woman who had previously reported benefit, experienced relief or demonstrated improvement of tremor following marijuana, despite central effects as evidenced by drowsiness or mild euphoria; no effects other than drowsiness and in two cases mild unsteadiness occurred after diazepam. However, in all five, similar improvement was seen after both levodopa and apomorphine, and in three cases tremor resolved completely.
These results do not support the notion that cannabis when smoked reduces tremor or any other Parkinsonian disabilities. The drug clearly has other effects and it may be that its non-specific sedative or anxiolytic actions benefit certain tremulous patients when anxiety is a significant trigger factor.