Nitrendipine is a medication used to treat high blood pressure and angina. Nitrendipine impurities refer to any unwanted or unintended substances present in the medication that may affect its safety or efficacy. These impurities can be produced during the manufacturing process or as a result of degradation over time. Therefore, it is important to monitor and control the levels of nitrendipine impurities to ensure the quality and safety of the medication.