Bosentan is an endothelin receptor antagonist used to treat pulmonary arterial hypertension. However, the drug may contain impurities that can affect its efficacy and safety. These impurities include Bosentan N-methyl impurity, Bosentan N-oxide impurity, and Bosentan related compound A. The presence of these impurities may lead to toxicity, reduced drug potency, or adverse effects on patient health. Therefore, it is important to monitor and control the levels of Bosentan impurities in drug products.