Exploring Differences in Pharmacometrics of Rabeprazole between Genders via Population Pharmacokinetic-Pharmacodynamic Modeling

Considerations of sex in bioequivalence assessments: does sex affect pharmacokinetic variability between evaluation formulations?

BACKGROUND

Bioequivalence assessment determines the equivalence between drug formulations and is primarily used to demonstrate that a generic product is equivalent to its reference. The sex of the drug consumer is a major consideration in bioequivalence assessment, but specific ratios or absolute criteria for sex composition are usually not specified.

PURPOSE

This study explored whether the sex of participants in a bioequivalence assessment could significantly affect the pharmacokinetic variability between formulations and decision outcomes. In bioequivalence studies, the sex composition should reflect the drug's target population, but it is often acceptable to limit it to healthy adult males. Therefore, it is essential to consider the variation in bioequivalence results according to sex.

METHODS

Levocetirizine and rabeprazole enteric-coated tablets were chosen as investigational agents, and clinical trial data for these were used in the bioequivalence analysis. This analysis was conducted both with and without considering sex, and the final determination of equivalence was based on whether the 90% confidence interval for the ratio of standard pharmacokinetic parameters between the reference and test formulations fell within the 80 to 125% range. Additionally, principal component analysis (PCA) was performed to determine whether there were significant differences in the targeted pharmacokinetic parameter values between drug formulations across each sex group.

RESULTS

Bioequivalence of levocetirizine's reference and test formulations was confirmed, independent of sex. For rabeprazole, bioequivalence was established in males-even without considering sex-but not in females, based on extended criteria for drugs with significant pharmacokinetic variability. The PCA results also showed that there were significant differences (P < 0.05) in the distribution of pharmacokinetic parameters of rabeprazole by gender and formulation. This indicates that equivalence assessments may vary based on pharmacokinetic differences related to sex among subjects in bioequivalence studies. Thus, it was shown that sex may influence pharmacokinetic variability between reference and test formulations of the same drug.

CONCLUSION

This study provided valuable insights into the role of sex in bioequivalence studies. For drugs exhibiting significant pharmacokinetic differences between sexes, it is crucial to recognize that bioequivalence results may vary based on the sex ratio in the participant group. Therefore, further analysis and interpretation, taking sex-related factors into account, will be necessary during bioequivalence evaluations.

Exploring gender differences in pharmacokinetics of central nervous system related medicines based on a systematic review approach

Due to the inevitable differences in physiological and/or genetic factors between genders, the possibility that differences in pharmacokinetics between genders may occur when exposed to the same dose of the same drug is subject to reasonable inference and suspicion. Nevertheless, a significant number of medicines still rely on empirical usage and uniform clinical application without consideration of inter-individual diversity factors. In particular, in the pharmacokinetic diversity of medicines related to central nervous system (CNS) activity, consideration of gender factors and access to comparative analysis are very limited. The purpose of this study was to conduct an integrated analysis and review of differences in pharmacokinetics between genders that have not been specifically reported to date for medicines related to CNS effects, which are a group of drugs with relatively significant concerns about systemic side effects. This study was accessible through extensive data collection and analyzes using a web-based scientific literature search engine of pharmacokinetic results of CNS-related drugs performed on humans, taking gender into account. As a result, significant differences in pharmacokinetics between genders were identified for many drugs related to CNS. And most of the pharmacokinetic differences between genders suggested a higher in vivo exposure in females. This study suggests that consideration of gender factors cannot be ignored and will be an important point of interest in the precision medicine application of CNS-related medicines.

Is Gender an Important Factor in the Precision Medicine Approach to Levocetirizine?

Currently, there is insufficient information on the variability in levocetirizine pharmacometrics among individuals, a crucial aspect for establishing its clinical use. The gender differences in pharmacokinetics and the extent of variation in pharmacodynamics have not been definitively identified. The primary goal of this study was to investigate gender differences in levocetirizine pharmacokinetics and quantitatively predict and compare how these gender-related pharmacokinetic differences impact pharmacodynamics, using population pharmacokinetic-pharmacodynamic modeling. Bioequivalence results for levocetirizine (only from the control formulation) were obtained from both healthy Korean men and women. Physiological and biochemical parameters for each individual were utilized as pharmacokinetic comparison and modeling data between genders. Pharmacodynamic modeling was performed using reported data on antihistamine responses following levocetirizine exposure. Gender, weight, body surface area, peripheral distribution volume, albumin, central-peripheral inter-compartmental clearance, and the fifth sequential absorption rate constant were explored as effective covariates. A comparison of the model simulation results showed a higher maximum concentration and faster plasma loss in females than in males, resulting in a faster recovery to baseline of the antihistamine effect; however, the absolute differences between genders in the mean values were not large within 10 ng/mL (for plasma concentrations) or % (wheal and flare size changes). Regarding the pharmacokinetics and pharmacodynamics of levocetirizine, the gender effect may not be significant when applying the usual dosage (5 mg/day). This study will be useful for bridging the knowledge gap in scientific precision medicine by introducing previously unconfirmed information regarding gender differences in levocetirizine pharmacometrics.