The effect of an intravenous injection of physostigmine salicylate (1 mg) on the extrapyramidal side effects of phenothiazine therapy was investigated in ten psychiatric patients. Six of the ten patients who had developed minimal rigidity or tremor or both during phenothiazine therapy exhibited a worsening of these neurological signs after the physostigmine injection. It is concluded that cholinergic hyperactivity or hypersensitivity or both occur in phenothiazine-induced Parkinsonism as well as idiopathic Parkinson disease.
Ambani LM, Van Woert MH, Bowers MB. Physostigmine Effects on Phenothiazine-Induced Extrapyramidal Reactions. Arch Neurol. 1973;29(6):444–446. doi:10.1001/archneur.1973.00490300106018
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