Displaying 13 results of Quinapril Impurities Quinapril is an ACE inhibitor used to treat high blood pressure and heart failure. However, during the manufacturing process of quinapril, certain impurities can be formed which can have adverse effects on human health. These impurities can include N-nitroso quinapril, quinaprilat diacid impurities, and other related impurities. It is important to monitor and control the levels of these impurities to ensure the safety and efficacy of the drug product.