Falsified tadalafil tablets distributed in Japan via the internet

The adverse health effects of falsified medicines for erectile dysfunction have been reported in Japan. We purchased tadalafil (Cialis) tablets online and assessed their authenticity and quality. Of the 45 samples we tested, nine were genuine, 23 were falsified, nine were unregistered/unlicensed samples, and the authenticity of four samples could not be ascertained. Observation of packaging and tablet size, weight, and color revealed differences between some genuine and falsified samples. All genuine samples contained the active pharmaceutical ingredient tadalafil at adequate quantities, while falsified samples contained sildenafil (Viagra). Some falsified samples contained insufficient quantities of tadalafil. All unregistered/unlicensed samples contained neither tadalafil nor sildenafil. Some falsified samples did not dissolve/disintegrate sufficiently. The status of most samples was detectable by Raman scattering and near-infrared spectroscopy. Restricting consumer access to falsified medicines can prevent undesirable health effects.