Assessing bioequivalence of generic antiepilepsy drugs
Article first published online: 29 JUN 2011
Copyright © 2011 American Neurological Association
Annals of Neurology
Volume 70, Issue 2, pages 221–228, August 2011
How to Cite
Krauss, G. L., Caffo, B., Chang, Y.-T., Hendrix, C. W. and Chuang, K. (2011), Assessing bioequivalence of generic antiepilepsy drugs. Ann Neurol., 70: 221–228. doi: 10.1002/ana.22452
- Issue published online: 5 AUG 2011
- Article first published online: 29 JUN 2011
- Accepted manuscript online: 12 APR 2011 08:20AM EST
- Manuscript Accepted: 1 APR 2011
- Manuscript Revised: 22 MAR 2011
- Manuscript Received: 3 NOV 2010
Patients with epilepsy are often concerned that switching between brand-name and generic formulations of antiepilepsy drugs (AEDs) may cause clinically significant changes in plasma drug concentrations. We assessed bioequivalence (BE) studies for approved generic AEDs to evaluate US Food and Drug Administration claims that: (1) generic AEDs are accurate copies of reference formulations; (2) delivery of reference formulations may be as variable as generic AEDs and so provide no increased benefit; and (3) switches between generic AED formulations are safe and effective.
We determined differences in 90% confidence interval limits for total drug exposure (AUC0-t) and peak concentration (Cmax) ratios of generic and reference formulations during fasting and fed BE studies. We simulated BE between generic formulations after adjusting for reference values.
AUC0-t values of approved reference and generic formulations differed by <15% in 99% of BE studies; Cmax differed by <15% in 89% of studies. Food affected variability of Cmax but not AUC0-t. Intersubject variability in Cmax and AUC0-t was small and similar for reference and generic products. In simulated switches between 595 pairs of generic AED formulations, estimated AUC0-t differed by >15% for 17% of pairs; estimated Cmax differed by >15% for 39%. AEDs with low bioavailability and solubility (eg, oxcarbazepine) had the greatest variability in BE.
Most generic AED products provide total drug delivery (AUC) similar to reference products; differences in peak concentrations between formulations are more common. Switches between generic AED products may cause greater changes in plasma drug concentrations than generic substitutions of reference products. ANN NEUROL 2011