Quality and Authenticity of Metformin Tablets Circulating on Japanese Websites

BACKGROUND: Low-quality medicines and falsified medicines represent long-standing problems in developing countries. In Southeast Asia, the circulation of low-quality diabetes drugs (metformin) has been confirmed. It is possible that low-quality metformin has entered Japan via personal import through the Internet. This study evaluated the pharmaceutical quality and authenticity of metformin tablets obtained via the Internet in Japan. METHODS: In total, 33 samples of 500-mg metformin tablets and 7 samples of extended-release/sustained-release tablets (500, 750, and 1,000 mg) were purchased via personal import in January 2017. Confirmation of a prescription was never requested purchase. The obtained samples were subjected to visual observations and authenticity investigations. Additionally, quantitative analysis, content uniformity and dissolution tests were performed using HPLC–PDA. RESULTS: Our authenticity investigations revealed that seven samples were genuine products, whereas the authenticity of the remaining 33 samples was unclear. Referring to United States Pharmacopeia 2014 for validation, four samples failed quality testing, five samples failed content uniformity testing, and two samples failed dissolution testing. CONCLUSIONS: Our findings illustrate that metformin tablets of poor-quantity and unregistered/unlicensed doses are available online and that it is important to increase consumer awareness about the presence of these medicines on the Internet to prevent the purchase of substandard medicines.