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May 1996

Antihistaminics in Idiopathic Dystonia

Author Affiliations

The Toronto Hospital Morton and Gloria Shulman Movement Disorder Centre 399 Bathurst St, MP11-306 Toronto, Ontario Canada M5T 2S8

Arch Neurol. 1996;53(5):405. doi:10.1001/archneur.1996.00550050027012

I read with interest the article by Truong et al1 describing a beneficial effect of diphenhydramine hydrochloride in 3 of 5 consecutive patients with idiopathic dystonia. The mechanism of action of diphenhydramine in these patients remains uncertain and the authors mention the possibility of anticholinergic effects (suggested as unlikely), histamine1-antagonist effects, and potential interactions with opiates. I should like to draw readers' attention to a study that we published in 19822 evaluating the short-term effects of parenteral injections of 2 drugs with anticholingeric properties: benztropine mesylate (with potent central antimuscarinic properties and a high capacity to block dopamine reuptake), and atropine sulfate (a classic anticholinergic lacking effects on dopamine reuptake) as well as chlorpheniramine maleate, a potent antihistaminic with less anticholinergic properties than benztropine and diphenhydramine. We studied the effects of single parenteral injections of the 3 drugs compared with normal saline placebo in a randomized

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