Abstract
Purpose
The existence of a sex-by-formulation interaction in bioequivalence studies implies that the bioequivalence results (i.e., the test/reference ratio of the pharmacokinetic parameters) obtained in one sex are not similar to those obtained in the other sex. Therefore, results obtained in studies including only males may not be representative of the results obtained in females and vice versa. The best evidence of the existence of a sex-by-formulation interaction has been obtained from a study conducted with transdermal patches. This observation might be caused by the different characteristics of the skin of males and females. The purpose of this work is to investigate the existence of a sex-by-formulation interaction in all bioequivalence studies of transdermal patches submitted to the Spanish Agency for Medicines between 2010 and 2016.
Methods
Only five different products (Buprenorphine-1, Fentantyl-1, Fentanyl-2, Rivastigmine-1 and Rivastigmine-2) that were submitted for registration included nine bioequivalence studies conducted in males and females. As single dose and multiple dose studies are required for registration of transdermal patches in the European Union, more than one study may be available to confirm the existence of a sex-by-formulation interaction.
Results
A sex-by-formulation interaction is suggested in six out of 27 datasets (22%), corresponding to two products, and it is statistically significant in three of them (11%).
Conclusions
The sex-by-formulation interaction detected in some pharmacokinetic parameters of some studies is excluded when the study is repeated, which shows that these results are not reproducible. There is no evidence to require bioequivalence demonstration for transdermal patches in males and females separately.
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Acknowledgements
The authors are grateful to Mr. Jesús Garrido for his assistance in the statistical analysis.
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A.G.-A., J.G. and E.G.-R. contributed to the conception of the work and the interpretation of the results. A.G.-A. and S.M. contributed in the acquisition of the data of the bioequivalence studies of transdermal patches submitted to the Spanish Agency for Medicines and Health Care Products. E.G.-R., J.M., F.A-S. and C.Á. conducted the analysis of the data.
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González-Rojano, E., Marcotegui, J., Morales-Alcelay, S. et al. Sex-by-formulation interaction in bioequivalence trials with transdermal patches. Eur J Clin Pharmacol 75, 801–808 (2019). https://doi.org/10.1007/s00228-019-02632-1
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DOI: https://doi.org/10.1007/s00228-019-02632-1