The quality of sildenafil active substance of illegal source.

There must be a large market for active pharmaceutical ingredients of illegal source to support the huge and lucrative business of trade in illegal medicines. The active substances found in illegal pharmaceuticals may differ from their legal counterparts concerning purity and associated risks for the health of the user. In this study we show two examples in which the active substance sildenafil, used in erectile dysfunction products, was not of European Pharmacopeia quality. In one case milligram-scale amounts of a 2-mercaptobenzothiazole contamination were found, in another case the mesylate salt rather than the monograph based citrate was used. For the user of products containing these active substances, the risks of side effects increase through the inherent properties of the impurity and the chance of overdosing. The fact that the users are most likely not aware of the poor quality of the products adds up to the health risk of using prescription medication without consulting medical professionals.