Displaying 7 results of Fesoterodine Fumarate Impurities Fesoterodine fumarate impurities are unwanted substances that may be present in fesoterodine fumarate drug products. These impurities can be formed during the synthesis or manufacturing process, or they may result from degradation of the active ingredient. The presence of impurities can affect the safety and efficacy of the drug, and therefore, it is important to monitor and control their levels. Regulatory authorities have established limits for impurities in drug products to ensure their quality and safety.