Generic replacement of clozapine: a simple decision model from a Canadian perspective

Increased incidence of relapse has been differences in relapse incidence. The difference at reported upon switching patients with schizophrenia from brand name to generic clozapine. The cost of treating relapsed patients could offset the reduced drug acquisition cost associated with switching. A decision model was designed to predict the relapse incidence at which switching to generic clozapine is cost-neutral.

A hypothetical cohort of 100 patients with schizophrenia stabilized on brand name clozapine was considered either to remain on the brand name product, or to switch to the generic version. Medication effectiveness data were taken from two reports following patients who underwent generic replacement of clozapine. Direct costs associated with each treatment were projected from a Canadian Ministry of Health perspective, considering drug acquisition and treatment of relapse. Unit costs were derived from published sources.

Direct costs of the two treatment regimens were compared based on which switching to generic clozapine would result in no direct cost saving was determined.

Switching a patient to generic clozapine would save 1241 Canadian dollars annually if the patient did not relapse, and would cost 9823 Canadian dollars if the patient relapsed. Assuming an 11% difference in relapse for patients taking brand name and generic clozapine, respectively, switching 100 patients to generic clozapine would save 24 Canadian dollars per patient. If the relapse difference for patients taking generic clozapine is 28%, the switch to the generic medication would cost 1857 Canadian dollars per patient. Switching patients from brand name clozapine to generic clozapine was predicted to be neutral to direct costs when the absolute difference in relapse incidence was 11.2%.

Switching to a generic medication may not always reduce direct costs. Physicians, patients and third party payers should consider the potential consequences before instituting generic replacement of clozapine for economic reasons.