Transl Clin Pharmacol.  2017 Dec;25(4):179-182. 10.12793/tcp.2017.25.4.179.

A post hoc analysis of intra-subject coefficients of variation in pharmacokinetic measures to calculate optimal sample sizes for bioequivalence studies

Affiliations
  • 1Department of Clinical Pharmacology and Therapeutics, Seoul National University College of Medicine and Hospital, Seoul 03080, Korea.
  • 2Department of Statistics, College of Natural Sciences, Seoul National University, Seoul 03080, Korea. youngjo@snu.ac.kr
  • 3Department of Clinical Pharmacology and Therapeutics, Seoul National University College of Medicine and Bundang Hospital, Seongnam 13620, Korea. jychung@snubh.org

Abstract

Because bioequivalence studies are performed using a crossover design, information on the intra-subject coefficient of variation (intra-CV) for pharmacokinetic measures is needed when determining the sample size. However, calculated intra-CVs based on bioequivalence results of identical generic drugs produce different estimates. In this study, we collected bioequivalence results using public resources from the Ministry of Food and Drug Safety (MFDS) and calculated the intra-CVs of various generics. For the generics with multiple bioequivalence results, pooled intra-CVs were calculated. The estimated intra-CVs of 142 bioequivalence studies were 14.7±8.2% for AUC and 21.7±8.8% for C(max). Intra-CVs of C(max) were larger than those of area under the concentration-time curve (AUC) in 129 studies (90.8%). For the 26 generics with multiple bioequivalence results, the coefficients of variation of intra-CVs between identical generics (mean±sd (min ~ max)) were 38.0±24.4% (1.9 ~ 105.3%) for AUC and 27.9±18.2 % (4.0 ~ 70.1%) for C(max). These results suggest that substantial variation exists among the bioequivalence results of identical generics. In this study, we presented the intra-CVs of various generics with their pooled intra-CVs. The estimated intra-CVs calculated in this study will provide useful information for planning future bioequivalence studies.

Keyword

bioequivalence; coefficient of variation; sample size; power; generic drugs

MeSH Terms

Area Under Curve
Cross-Over Studies
Drugs, Generic
Sample Size*
Therapeutic Equivalency*
Drugs, Generic

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