Abstract Phosphodiesterase type 5-inhibitor (PDE5-i) such as sildenafil and its analogues are among the most popular medicines bought through online retailers. Many reports however show that these products often are of poor quality or do not have a marketing authorization in the recipient country and thus may pose serious health threats to consumers. Qualitative and quantitative investigations were carried out on two quality attributes of sildenafil-labelled tablets, seized by the Luxembourgish customs from 2016 to 2020: sildenafil content and presence of undeclared active pharmaceutical ingredients (API). 649 samples, predominantly bought in India, were investigated. Results indicate an overall quality increase over the 5 years, but still 46.4% of the analysed samples were not conform to standard European quality regulations, with 18.2% of the products contaminated with at least one undeclared active pharmaceutical ingredients and 35.1% having a sildenafil content significantly different from claimed dosage.Despite an overall increase in quality over the last 5 years, many samples still contain adulterants with potentially serious health risks or non-conform API concentrations.
Keywords Sildenafil, Quality assessment, Contaminants, Substandard medicines.