Terlipressin impurities are the unwanted substances that may be present in terlipressin drug products. These impurities can affect the quality, safety, and efficacy of the drug. It is critical to control and limit the levels of terlipressin impurities to ensure the drug's purity and effectiveness. Analytical techniques such as high-performance liquid chromatography (HPLC) and mass spectrometry (MS) are used to identify and quantify terlipressin impurities. Regulatory bodies such as the FDA have established maximum limits for the levels of terlipressin impurities in drug products.