Their treatment is mostly simple and very effective. Parenteral administration of anticholinergics such as beztropine or diphenhydramine is reported to reverse drug-induced dystonias promptly. Antihistamines having anticholinergic action are also, such as promethazine, helpful; they inhibit the neurotransmitter acetylcholine level in the brain. In some cases benzodiazepines are found to be useful. Usually, anticholinergic drugs are continued for a week to prevent recurrence.