Branded versus generic clozapine: Bioavailability comparison and interchangeability issues

F. Y.W. Lam, L. Ereshefsky, G. B. Toney, C. Gonzales

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


Clozapine has been the treatment of choice for patients with refractory schizophrenia. Generic clozapine has recently become available, because of a waiver of the usual criteria for establishing bioequivalence. However, there are biopharmaceutical, bioavailability, and clinical concerns related to the generic formulation raised by both clinicians and academic researchers. We conducted a prospective, randomized, crossover study to evaluate steady-state pharmacokinetics, pharmacodynamics, and tolerability of generic clozapine (Zenith Goldline Pharmaceuticals) versus Clozaril (Novartis Pharmaceuticals) in schizophrenic patients. A preliminary report of the pertinent bioavailability results is presented here. Despite comparable mean plasma concentration-time curves, significant differences were found in the primary pharmacokinetic parameters of the 2 formulations in almost 40% of patients. Such intraindividual differences raise the issue of average bioequivalence versus individual bioequivalence and the implication for interchangeability of different clozapine formulations. The decision to switch a patient from branded to generic clozapine should be made on an individual basis with special emphasis on clinical outcome, and patients should be monitored closely during the transition.

Original languageEnglish (US)
Pages (from-to)18-22
Number of pages5
JournalJournal of Clinical Psychiatry
Issue numberSUPPL. 5
StatePublished - 2001

ASJC Scopus subject areas

  • Psychiatry and Mental health


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