Endothelin receptor antagonists What are endothelin receptor antagonists? Endothelin receptor antagonists (ERAs) are a type of targeted therapy used to treat people with pulmonary hypertension (PH). Targeted therapies slow the progression of PH and may even reverse some of the damage to the heart and lungs. There are now three types of ERA currently used to treat PH: ambrisentan (Volibris) bosentan (Tracleer and now “generic” i.e. not branded) macitentan (Opsumit) All ERAs are taken as tablets. How do endothelin receptor antagonists work? ERAs work by reducing the amount of a substance called endothelin in the blood. Endothelin is made in the layer of cells that line the heart and blood vessels. It causes the blood vessels to constrict (become narrower). In people with PH the body produces too much endothelin. This causes the blood vessels in the lungs to become narrow, increasing the blood pressure in the pulmonary arteries. ERAs reduce the amount of endothelin in the blood, therefore limiting the harm an excess of endothelin can cause. Precautions when taking endothelin receptor antagonists Liver function tests If you are taking any of the three ERAs, you will need regular blood tests to make sure your liver is not being harmed. These blood tests can show if your liver will become damaged if you carry on taking the drug. Your PH specialist team will discuss the risks associated with taking ERAs with you. If you are female, this may include the risks of taking ERAs in pregnancy.