There are few objective guidelines for the clinician in the choice of antiparkinsonian drugs, even though these drugs are a heterogeneous group. We compared the effect of biperiden (M1 selective anticholinergic) and amantadine (dopaminergic) on neuroleptic-induced parkinsonian extrapyramidal symptoms (EPS) and tardive dyskinesia (TD)-type involuntary movements.
Thirty-two schizophrenic (DSM-III-R) inpatients on long-term stable antipsychotic and trihexyphenidyl treatment entered the study. Antipsychotics were kept constant, but trihexyphenidyl was replaced by placebo under single-blind conditions for 1 week, and the the patients were randomly assigned to either amantadine 100 mg b.i.d. or biperiden 2 mg b.i.d. treatment under double-blind conditions for 2 weeks. After a second 1-week placebo period, the test drugs were crossed over under double-blind conditions. Assessments of tardive dyskinesia (Abnormal Involuntary Movement Scale [AIMS]) and of parkinsonian extrapyramidal side effects (Simpson-Angus Neurologic Rating Scale) were made pretreatment and posttreatment.
Twenty-six patients completed all study procedures. Amantadine and biperiden were equally effective in relieving neuroleptic-induced EPS and did not exacerbate TD-type movements. AIMS scores during treatment were significantly lower than during placebo period. The findings were similar in patients with diagnosable TD.
Amantadine and biperiden have similar effects on neuroleptic-induced EPS and TD and may ameliorate mild TD.