Chiral bioanalytical methods in bioequivalence studies of intravenous vs. oral formulations of ibuprofen.

According to the Ibuprofen Product-Specific Bioequivalence Guidance of the European Medicines Agency, achiral bioanalytical methods are considered acceptable for demonstration of bioequivalence of ibuprofen-containing products. The aim of this investigation is to compare the bioequivalence outcomes obtained with individual R and S ibuprofen enantiomers and the sum of both enantiomers from bioequivalence studies in which new intravenous ibuprofen products were compared with oral ibuprofen products. Bioequivalence was assessed for S and R enantiomers of ibuprofen and the sum of both enantiomers, which was calculated to represent the results that would have been obtained with an achiral assay. The infusion rates of 15, 20, and 30 minutes modify the maximum concentration (Cmax ) of the intravenous administrations. In contrast, the time when the maximum concentration is observed (Tmax ) was insensitive to detect differences in input rate within this range of infusion times. The eutomer S-ibuprofen is the least sensitive analyte to detect differences in input rate; therefore, the regulatory acceptance of achiral bioanalytical methods for ibuprofen bioequivalence studies is justified because the sum of both enantiomers is more discriminative than the chiral methods where only the eutomer is used for regulatory decisions.

Investigation on the Existence of Sex-By-Formulation Interaction in Bioequivalence Trials.

The US Food and Drug Administration recommends that if a drug product is intended for use in both sexes, similar proportions should be recruited for bioequivalence (BE) studies. In contrast, in Europe, subjects can belong to either sex. Literature suggesting the existence of sex-by-formulation interaction (S × F) is limited to few studies. To investigate if S × F is observed, this work includes 120 BE studies. Differences larger than 20% between the ratio test/reference of women and men or statistically significant S × F occurred in 25 of 120 studies (20.8%). The prevalence is higher in small studies (36.00% vs. 16.8%). Large differences between the ratios of the sex groups are the tails of the distribution. Two studies were repeated, and the differences between the ratios of the sex groups disappeared. The 90% confidence intervals of S × F did not confirm any relevant S × F. There is no evidence to require studies in both sex groups, combined or separately.

Sex-by-formulation interaction in bioequivalence trials with transdermal patches.

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.

Evaluation of sex-by-formulation interaction in bioequivalence studies of efavirenz tablets.

AIMS: 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 would not be representative of the results that would have been obtained in females and vice versa. Recently, a sex-by-formulation interaction has been reported in a study for efavirenz tablets. The purpose of this paper is to investigate whether a sex-by-formulation interaction is actually observed in the bioequivalence studies conducted with efavirenz tablets. METHODS: The existence of sex-by-formulation interaction was investigated in the two studies conducted in our centre, where the same test and reference products were investigated in a pilot study with 12 subjects and a pivotal study with 36 subjects. RESULTS: In the pilot study, the point estimates for the test/reference ratio of geometrics means of Cmax in females and males were more than 20% different (95.42% vs.79.38%, i.e., 120.21%), but in a subsequent pivotal study the difference was less than 2% (111.14% vs. 109.98%, i.e., 101.66%). CONCLUSIONS: A sex-by-formulation interaction is suggested in the study with a small sample size, but it disappears when the study is repeated with a larger sample size. In conclusion, the analysis of subgroups should be conducted with caution when the size of the subgroups is not powered to show bioequivalence. There seems to be no reason to require bioequivalence studies for efavirenz in both sexes.