Plasma pooling to expedite bioequivalence estimation of rifampicin in fixed dose combinations.

Rifampicin has been found to be one of the most important antitubercular drugs; however, variable bioavailability of rifampicin in some fixed dose combinations (FDCs) as well as separate formulations has been reported in the literature. This resulted in proper evaluation of FDCs with standard protocol for bioequivalence trials. Earlier, plasma pooling as a rapid method for bioequivalence assessment of rifampicin in FDCs was proposed from our laboratory. Results obtained after pooled plasma sample analysis were compared with those from the individual plasma sample analysis. Case studies from our laboratories further validate and support the use of plasma pooling method as a faster and cost effective tool for bioequivalence assessment of rifampicin in FDCs, which will be useful in order to speed up the registration and approval of good quality FDCs.

Determination of rifampicin bioequivalence in a three-drug FDC by WHO and indian protocols: effect of sampling schedule and size.

SETTING: To promote the quality assurance of fixed-dose combination (FDC) formulations, the World Health Organization (WHO) has prepared a convenient simplified protocol for the determination of rifampicin (RMP) bioequivalence. During the development of this protocol, it was proved that sampling time up to 8 h can determine the rate and extent of RMP absorption. However, this protocol utilises 20 volunteers in contrast to other local regulatory requirements of a minimum of 12 volunteers. The different sample sizes utilised in these protocols may affect the sensitivity of the bioequivalence outcome. OBJECTIVE: To determine the effect of sampling size and schedule on RMP bioequivalence when two different protocols are used. DESIGN: A bioequivalence trial was conducted with a study design of 20 volunteers and 24 h sampling time, which fulfils the requirements of both the WHO and Indian regulatory protocols. Pharmacokinetic and statistical analysis was done by stepwise reduction in sample size and schedule. RESULT: Bioequivalence limits of RMP were unaffected by a reduced sample size of 12 volunteers and 8 h sampling time. CONCLUSION: Minimising sample size after validation for borderline and poor quality FDC formulations can further reduce the cost of conducting bioequivalence trials.

Establishment of a reference formulation for bioequivalence assessment of rifampicin-containing FDCs: an essential step towards improving tuberculosis treatment.

SETTING: Selection of a reference product for bioequivalence studies of rifampicin (RMP) in prequalifying fixed-dose combinations (FDC) for worldwide distribution through the WHO is critical. OBJECTIVE: To investigate the feasibility of establishing FDC formulations as reference products for bioequivalence studies of RMP in prequalification programmes. DESIGN: A biostudy was conducted as an open, two-period randomised cross-over trial. Two three-drug FDCs containing RMP, isoniazid and ethambutol hydrochloride were administered to a group of 22 volunteers with a wash-out period of 1 week. Plasma samples were collected and analysed for the concentration of RMP and desacetyl-RMP, a major active metabolite of RMP, up to 24 h. Pharmacokinetic parameters of RMP were calculated: Cmax, AUC0-24, Tmax, kel and absorption efficiencies. RESULTS: No significant difference was observed between the administered formulations with respect to the major pharmacokinetic parameters Cmax, Tmax and AUC0-24 when evaluated by parametric (two-way ANOVA) and non-parametric (Hauschke's analysis) statistical analysis. The concentration of RMP falls within the reported acceptable therapeutic range. CONCLUSION: FDCs can be developed as a reference product for bioequivalence studies.

Plasma pooling: utility in expediting bioequivalence assessment of rifampicin-containing fixed-dose combinations.

To improve the rapidity of the registration process of rifampicin (RMP) containing fixed-dose combination (FDC) formulations, a plasma pooling methodology was used to increase the throughput of bioanalysis of plasma samples from bioequivalence trials of FDCs. Plasma samples of a biostudy were analysed for RMP using traditional analysis methods as well as a plasma pooling method (volunteer and time pooling). Both methods produced similar results, with less than 15% variability in both volunteer and time pooling. The plasma pooling method for bioanalysis was validated. Further studies are required to identify and reduce the percentage variability.

Quality control of anti-tuberculosis fixed-dose combination formulations in the global market: an in vitro study.

OBJECTIVE: To determine the quality, and especially the dissolution properties of rifampicin, of fixed-dose combination (FDC) formulations of anti-tuberculosis agents manufactured by major market holders in the anti-tuberculosis sector and supplied for use in national tuberculosis control programmes. METHODS: Dissolution studies were performed for four formulations supplied by four different manufacturers in four dissolution media (0.1N and 0.01N HCl, phosphate buffer [PB] and 20% vegetable oil in PB), at four different agitation rates using USP apparatus II. The formulations were subjected to 4-week accelerated stability studies (40 degrees C / 75% RH) and evaluated for physical, chemical and dissolution stability. RESULTS: The formulations tested complied with pharmacopeial quality control (QC) tests. The extent of rifampicin release was independent of dissolution medium; however, a slight decrease in the dissolution rate was observed in two products. More than 75% of drug was released in 45 min at all agitation intensities except 30 rpm, and 20% oil in the medium reflected fed state. Formulations were stable in the packaging conditions recommended by the manufacturer for at least 4 weeks. CONCLUSIONS: The formulations tested passed the QC tests and were found to be stable. A decrease in the rate, although not the extent, of dissolution necessitated multiple point dissolution in gastric and intestinal pH conditions to ensure consistency in in vivo bioavailability.

Bioequivalence assessment of rifampicin, isoniazid and pyrazinamide in a fixed dose combination of rifampicin, isoniazid, pyrazinamide and ethambutol vs. separate formulations.

Depending on the patient category, tuberculosis requires treatment with 3 to 5 drugs which means that patient's compliance to therapy may not be optimal. To increase patient's adherence to treatment schedules, these drugs can be given as single drug preparations or fixed dose combinations (FDCs) of 2 or more drugs in a single formulation. However, an important issue associated with a rifampicin-containing FDC is its quality. Hence, to avoid spurious formulations entering the market, the World Health Organization and the International Union Against Tuberculosis and Lung Disease have recommended FDCs only of proven bioavailability. In this study, the relative bioavailability of rifampicin, isoniazid and pyrazinamide was assessed in a group of 14 healthy male subjects using the FDC tablet containing 4 drugs versus separate formulations at the same dose levels. The study was designed as an open, crossover trial. A total of 9 blood samples were collected over a period of 24 h. The concentration of rifampicin, its main metabolite desacetyl rifampicin, isoniazid and pyrazinamide in plasma were assessed using HPLC analysis. The pharmacokinetic parameters AUC(0-24) and Cmax were subjected to parametric and non-parametric statistical tests at 90% confidence interval. In addition, time to reach peak concentration (tmax), elimination rate constant (Kel) and terminal elimination half-life (t1/2) for each drug were also calculated. It was concluded that the FDC tablet containing 4 drugs is bioequivalent to separate rifampicin, isoniazid and pyrazinamide formulations at the same dose levels.