Displaying 4 results of Selamectin Impurities Selamectin is a medication used to treat parasitic infestations in dogs and cats. However, during the manufacturing process, impurities may be formed which can affect the quality and safety of the drug. Selamectin impurities can include products of incomplete synthesis, degradation products, and contaminants. These impurities need to be identified, characterized, and controlled to ensure the safety and efficacy of the medication.