Three Cebus apella monkeys were treated with biweekly
injections of
fluphenazine enanthate for 1 year. Two distinct motor syndromes were produced. The first consisted of acute dystonic, dyskinetic, parkinsonian, and
akathisia-like reactions, which worsened after each injection, were not exacerbated by
drug withdrawal, and could be abolished or prevented with
benztropine. The second appeared after cessation of
neuroleptic treatment and consisted of
abnormal movements very similar to those of patients with
tardive dyskinesia (TD). This syndrome was abolished completely by reinstitution of
fluphenazine treatment. One monkey was given a second and third course of
fluphenazine, each course lasting 4 weeks. The second syndrome was seen after but not during each course and remained robust for a longer period after the third than after the first or second courses of treatment. We conclude that the first syndrome is analogous to the early appearing extrapyramidal symptoms of
neuroleptic-treated patients and that, according to preliminary evidence, reversible TD may turn into irreversible TD with continued periods of on and off
neuroleptic treatment.