Dystonic reactions following neuroleptics: time course and proposed mechanisms.

The occurrence of acute dystonic reactions was studied relative to drug pharmacokinetic parameters following a single dose of the phenothiazine, butaperazine. Dystonias occurred more than one half-life from peak butaperazine levels, 23 to 56 h after drug administration. The authors postulate that the appearance of dystonias on falling plasma concentrations may be due to disruption of dopaminergic-cholinergic balance caused by differential antidopaminergic and anticholinergic potencies of the drug.