Displaying 10 results of Promethazine Impurities Promethazine is a commonly used antihistamine medication that helps relieve symptoms of allergies and motion sickness. However, like most drugs, it can have impurities that can affect its safety and efficacy. These impurities can occur during the manufacturing process, transportation, or storage. It is essential to identify and control these impurities to ensure the quality and safety of the medication. Some common impurities found in promethazine include related substances, residual solvents, and degradation products.