Antipsychotic prescribing patterns and the treatment of extrapyramidal symptoms in older people.

Objectives: We have previously identified antipsychotic use as a risk factor for the use of both dopaminergic and anticholinergic antiparkinsonian drugs in older people. This study examines whether and how such antipsychotic regimens were adjusted before the addition of an antiparkinsonian drug.
Design: Retrospective comparison study
Participants: There were 1307 antipsychotic users begun on anticholinergic antiparkinsonian drugs and 345 antipsychotic users begun on dopaminergic drugs; 1864 antipsychotic users not prescribed antiparkinsonian drugs served as comparison subjects. Data were drawn from health care claims of patients aged 65-99 in the New Jersey Medicaid Program from 1981 to 1990.
Measurements: We determined if antipsychotic regimens were discontinued, reduced in dosage, or modified to reduce extrapyramidal toxicity before the institution of antiparkinsonian therapy.
Results: Thirty-five percent of the patients begun on dopaminergic drugs had their antipsychotic medication discontinued before beginning antiparkinsonian therapy; the antipsychotic was discontinued in only 12% of patients who started anticholinergic medications (P < .001). Among the smaller subset of patients with sufficient duration of antipsychotic exposure to examine changes in dose, 54% of patients begun on dopaminergic agents had their antipsychotic regimen reduced or discontinued before antiparkinsonian therapy, whereas 33% of patients begun on anticholinergic agents had one of these regimen changes (P < .001). Controlling for potential clinical and demographic confounders using multivariate logistic regression did not substantively alter these results.
Conclusions: These data indicate that physicians frequently fail to discontinue or modify an antipsychotic regimen before adding a new drug to treat probable drug-induced extrapyramidal symptoms. Such prescribing patterns preceding use of dopaminergic antiparkinsonian drugs suggest that addition of such drugs may represent an inappropriate attempt to treat presumed idiopathic Parkinson's disease in many cases.