From conventional to atypical antipsychotics and back: dynamic processes in the diffusion of new medications

Abstract

Objective: Between 1994 and 1997, the Food and Drug Administration approved three new atypical antipsychotic medications for the treatment of schizophrenia. The authors tracked prescription patterns for these medications, an atypical antipsychotic approved in 1989, and conventional neuroleptics in the Department of Veterans Affairs (VA) to determine how the new drugs have diffused in a national health care system.

Method: Pharmacy claims data were collected for all patients with a diagnosis of schizophrenia in the VA. Patients who received stable 3-month prescriptions of any antipsychotic medication were followed over fiscal year 2000 to determine how often they were switched to another drug, how much time elapsed before they were switched, the drug to which they were switched, and whether they subsequently switched back to the original drug.

Results: Of the 21,873 patients with schizophrenia who had stable 3-month prescriptions of any antipsychotic medication, 5,426 (25%) had their medications switched during the next year. Half of these patients (N=2,708) switched back to their original drug, usually within 30 days. Patients who had stable prescriptions of clozapine were the least likely to be switched (18%), and patients who had stable prescriptions of quetiapine were the most likely to be switched (37%). When medications were switched, 35% of the patients were switched to olanzapine; only 1% were switched to clozapine, and only 14% were switched to quetiapine.

Conclusions: Pharmacotherapy for schizophrenia is a dynamic process. One-quarter of patients with stable antipsychotic drug regimens had their medication changed within 1 year. Quetiapine was the least prescribed of the newer drugs. These results suggest that it is important that all of these medications are included in formularies.