National prescribing patterns in the management of extrapyramidal symptoms among patients with schizophrenia

Antipsychotics, particularly typical agents, have been shown to cause extrapyramidal symptoms (EPS). We hypothesized a negative association between concomitant (at same visit) prescriptions for atypical antipsychotics and prescriptions for medications to manage EPS.

We combined National Ambulatory Medical Care Survey (NAMCS) data from 1993 through 1999 for visits by patients with a diagnosis of schizophrenia (ICD-9 295.0-295.9), that included a prescription for either an atypical or typical antipsychotic (but not both). We also constructed two, scale-weighted logistic regression models to separately estimate the odds and probabilities of receiving prescriptions for an antipsychotic and for a medication used to treat EPS.

From 1993 through 1999, there were an estimated 10,475,507 office visits with schizophrenia as a diagnosis; 7,371,625 (70.4 percent) included a prescription for a conventional (typical) antipsychotic. Thirty-four percent of visits included a prescription for a medication used to treat EPS. Being in the older age group, having Medicaid as primary coverage, belonging to an HMO, and being female significantly reduced the probability of receiving an atypical antipsychotic by 12.6 percent, 10.9 percent, 15.1 percent and 10.2 percent, respectively. Caucasian patients were 14 percent more likely to be prescribed an atypical. Antipsychotic type had a clinically and statistically significant effect on EPS management prescribing. A prescription for an atypical antipsychotic reduced the probability of receiving a concomitant prescription for EPS management by 26.8 percent.

As expected, we observed the hypothesized joint prescribing pattern. The results ofthis study suggest that atypical antipsychotic prescriptions strongly predict fewer prescriptions for EPS treatment, and, by implication, reduced need for EPS treatment in actual ambulatory care practices throughout the nation.