Antipsychotic drug exposure in a health maintenance organization.

In this study, exposure to antipsychotic drugs among ambulatory health maintenance organization (HMO) members is described. The diagnoses and mental health utilization associated with their use are explored, and concomitant drug use is investigated. The antipsychotic prescriptions were retrieved from an automated outpatient pharmacy data base for 2 years. Diagnoses for a two-percent sample of users were retrieved from an automated outpatient utilization data base. During the 2 years, 1,959 HMO members received 10,361 prescriptions for antipsychotics. Fifty-eight percent were female, and the mean age of users was 62 years of age. Haloperidol and thioridazine were the most frequently received drugs. Mean annual exposure to antipsychotics was 0.43% of the HMO population; estimated duration of exposure was 170 days; and estimated mean daily dose was 176 mg of chlorpromazine equivalents. Duration of exposure and mean daily dose were directly related. Both were also related to sex and age of users. Antipsychotic users were more likely to be exposed to various therapeutic classes of drugs indicative of chronic diseases. Antipsychotic exposure among ambulatory HMO members appeared to be conservative in terms of prevalence and similar to national experience in terms of daily dose. Estimated days of exposure appeared to place some users at increased risk of developing tardive dyskinesia, and the frequent and varied concomitant drug exposures can complicate treatment.