Penciclovir Impurities are the unwanted substances that are present in the Penciclovir drug during its synthesis or manufacturing process. Impurities may arise due to the use of raw materials, reagents, or solvents. These impurities can affect the quality, safety, and efficacy of the drug. Therefore, it is important to identify, monitor, and control the impurities in Penciclovir to ensure its purity and effectiveness.