Detection of Outlying Subjects in Bioequivalence Trials

Evaluation of veterinary medicinal products is one of the important areas where bioequivalence trials are conducted. One of the problems commonly encountered in bioequivalence trials is outlying subjects. These outlying data may occur either as unexpected observations or as the unusual subject who has extremely high or low bioavailability with respect to the reference formulation and may have dramatic effects on the bioequivalence test. Therefore, it is important to examine the data carefully for identification of outlying observations in bioequivalence studies. In this study we have developed another general approach, termed the Estimated Distance (ED), to the outliers’ detection problem.

Bioequivalence of Two Oral Formulations of Ciprofloxacin 250 mg Tablets in Healthy Mexican Volunteers

Background. There are numerous reports of low-quality formulations of ciprofloxacin in the market, which has been associated with therapeutic failure and the development of microbial resistance. Objective. The aim of this study is evaluating the bioequivalence between two oral immediate-release ciprofloxacin 250 mg tablets. Material and Methods. The study was performed in 24 Mexican healthy volunteers following a randomized cross over 2 × 2 design. Single doses of a test formulation Lemyflox® (Lemery Laboratories, Mexico) and the reference formulation Ciproxina® (Bayer, Mexico) were administered; blood samples were obtained during a 12 h period. Ciprofloxacin plasma concentrations were quantified using a validated High-Pressure Liquid Chromatography (HPLC) method, plasma concentration against time curves were constructed and pharmacokinetic parameters were determined by non-compartmental analysis. In order to determine bioequivalence, test/reference ratios of Cmax, AUC0-t and AUC0-inf were compared using analysis of variance (ANOVA), followed by the 90 % confidence intervals and the Schuirmann bilateral test. Results. The 90 % confidence intervals limits ranged from 82.92 to 100.88 % for Cmax, from 93.05 to 109.15 % for AUC0-t and from 97.76 to 114.99 % for AUC0-inf, all cases were within bioequivalence acceptance range of 80 - 125 %. Schuirmann test confirmed such observation as the probability that Cmax, AUC0-t and AUC0-inf ratios were beyond 80 - 125 % was lower than 0.05. Conclusions. The results obtained demonstrate bioequivalence between the test and reference formulations.

METHOD VALIDATION OF RIFAMPICIN ANALYSIS IN HUMAN PLASMA AND ITS APPLICATION IN BIOEQUIVALENCE STUDY

Objective: This research aims to validate the method for rifampicin analysis in plasma by using High-Performance Liquid Chromatography (HPLC) that can be used to study the bioequivalence of a generic tablet of rifampicin 450 mg “X” marketed in Indonesia. Methods: Bioequivalence test was analysed using HPLC equipped with UV-Vis detector at 377 nm. The mobile phase used was acetonitrile-phosphate buffer pH 6.8 (45:55) delivered at a flow rate of 1.5 ml/min. Bioequivalence test was conducted on a limited number of subjects (n=8). The subjects were divided into two groups randomly. The pharmacokinetic profiles of the test tablet and reference tablet were statistically calculated using SPSS program to see the test tablet and reference tablet were bioequivalence or not. Results: The developed HPLC method for rifampicin analysis in plasma was sufficiently valid based on the International Conference on Harmonization (ICH) and European Medicines Agency (EMA) guideline, with precision and accuracy values were % Relative Standard Deviation (% RSD = 1.40–13.04) and % Recovery (86.24–102.13), respectively. Meanwhile, the method was linear over studied concentration (0.05 to 10.26 µg/ml) with a coefficient of determination (R2) = 0.9984. The method also had good stability and sensitivity. The result of statistical calculation showed that the generic rifampicin tablet X was bioequivalence toward the reference tablet Rimactan 450 mg. Conclusion: The test rifampicin tablet that was, the generic tablet “X” was bioequivalence toward the reference rifampicin tablet “Rimactan”.

A Bioequivalence Test by the Direct Comparison of Concentration-versus-Time Curves Using Local Polynomial Smoothers

In order to test if two chemically or pharmaceutically equivalent products have the same efficacy and/or toxicity, a bioequivalence (BE) study is conducted. The 80%/125% rule is the most commonly used criteria for BE and states that BE cannot be claimed unless the 90% CIs for the ratio of selected pharmacokinetics (PK) parameters of the tested to the reference drug are within 0.8 to 1.25. Considering that estimates of these PK parameters are derived from the concentration-versus-time curves, a direct comparison between these curves motivates an alternative and more flexible approach to test BE. Here, we propose to frame the BE test in terms of an equivalence of concentration-versus-time curves which are constructed using local polynomial smoother (LPS). A metric is presented to quantify the distance between the curves and its 90% CIs are calculated via bootstrapping. Then, we applied the proposed procedures to data from an animal study and found that BE between a generic drug and its brand name cannot be concluded, which was consistent with the results by applying the 80%/125% rule. However, the proposed procedure has the advantage of testing only on a single metric, instead of all PK parameters.