Evaluation of bioequivalence between generic and brand-name clozapine in Chinese schizophrenic patients:...

Clozapine is the most effective therapy for schizophrenia. This study compared the bioequivalence of a generic formulation of clozapine (ChangZhou Pharmaceutical Factory Co. Ltd. Jiangsu, China) to the brand name formulation (Clozaril, HLS Therapeutics, Inc., Philadelphia, PA, USA) after multiple doses in Chinese schizophrenic patients.

This was a randomized, open-label, multiple-dose, 2-way crossover study in which patients with schizophrenia received the generic clozapine or Clozaril 100 mg twice daily for 10 days before crossing over to the alternate formulation for the next 10 days. Blood samples were collected at regular intervals during each treatment period, and plasma concentration of clozapine was determined by high-performance liquid chromatography.

26 patients were enrolled, of whom 24 completed the study and were included in the steady-state analyses. The mean AUC_0-12 was 6,003.29 h×ng/mL for generic clozapine and 6,347.53 h×ng/mL for Clozaril. The mean C_max,ss was 698.52 ng/mL for generic clozapine and 739.75 ng/mL for Clozaril. The ratio of the adjusted geometric means and its 90% CI of the ratios for AUC_0-12 was 96.24% (89.60 - 103.36%), and for C_max,ss was 95.90% (88.91 - 103.44%). A total of 66 adverse events were reported by 22 (84.62%) subjects. Among them, 34 occurred in 17 (65.38%) patients during dosing of generic clozapine, and 32 occurred in 16 (61.54%) patients during dosing of brand-name clozapine.

The result demonstrated that the generic clozapine was bioequivalent to brand-name clozapine (Clozaril). This would provide physicians with reassurance that patients who receive the studied generic clozapine will achieve similar plasma drug concentrations to those of brand-name clozapine (Clozaril).