Converting patients from brand-name clozapine to generic clozapine

To evaluate safety and dosage requirements when patients taking brand-name clozapine (Clozaril, Novartis Pharmaceuticals) are converted to generic clozapine (Zenith Goldline).

In November 1999, patients at Colorado Mental Health Institute at Pueblo taking Clozaril were changed to generic clozapine. Seventeen patients had been prescribed Clozaril for three years and were included in the study. Drug dosage, white blood cell (WBC) count values, and adverse drug reaction reports were compared. Data regarding patients on the brand-name product were evaluated retrospectively for the months of November, December, January, and February during the years 1996/1997, 1997/1998, and 1998/1999. These data were compared with those from the same patients after switching to generic clozapine for the same months in 1999/2000. A one-year comparison of brand-name (1998/1999) with generic drug (1999/2000) was also performed. Statistical analysis included a standard test comparing WBC values and a Brown-Forsythe test for comparing dosages.

There were no differences between the values obtained for the brand-name and generic products. WBC counts for the three-year data resulted in a p value of 0.9992. There was no difference when comparing the samples one year prior to switching and after the switch (p = 0.9991). There was no difference in dosages at three years or one year (p = 0.9999 and p = 0.9993, respectively). No adverse events were noted with the generic product.

No differences were found between the brand-name and generic clozapine groups with regard to WBC count, dosage, and adverse events. The conversion to the generic product is projected to save the pharmacy $90,000 annually.