In vitro equivalence of generic and branded amoxicillin tablet by microbiological assay method

Indonesian Ministry of Health advocate doctors, especially in government-owned healthcare facility, to prescribe generic drugs including amoxicillin. Although BPOM (the National Agency of Drug and Food Control) already guarantees that the generic amoxicillin and the branded one were interchangeable, lack of confidence in generic drugs still remains among patients, pharmacists, and doctors. This issue supported by lack of publication confirmed the therapeutic equivalence of branded and generic drugs. This study aims to evaluate and compare the in vitro microbiological assay of different generic and branded amoxicillin that are available in Indonesian market, especially those used in government-owned healthcare facilities. Microbiological assays for five samples of amoxicillin tablet containing 500 mg amoxicillin available in Indonesia were determined using a method from Indonesia Pharmacopeia. Samples were coded as Products A to E. The assay was carried out by measuring the diameter of the inhibition zones in the plate agar incubated with Escherichia coli and Staphylococcus aureus. The obtained data were evaluated to determine the sample potency and compared with the amoxicillin reference standard. Minor and insignificant differences (p > 0.05) were found in the diameters of the inhibition zones. Potency ratio measured both in E. coli and S. aureus were all between 95% and 105%. The lowest of the tested samples were from Product C, which resulted to ratio potencies of 96.3% and 95.5% in E. coli and S. aureus, respectively. All five samples were in the range of the acceptance criteria. Therefore, from the view of the microbiological assay, these products are in equivalence in quality and are interchangeable.