Endothelial receptor antagonists are oral medications commonly used to treat pulmonary arterial hypertension (PAH) linked to scleroderma. They are also being evaluated to possibly treat Raynaud’s phenomenon, a common symptom of systemic scleroderma.

Scleroderma is an inflammatory condition where patients have an abnormal build-up of scar tissue in different tissues and organs, such as the skin, lungs, heart, and intestinal tract.

How endothelin receptor antagonists work

PAH is a common and serious complication in people with systemic scleroderma, resulting in unusually high pressure in vessels supplying blood to the lungs. If left untreated, pulmonary arterial hypertension can cause heart failure.

Increased blood pressure in PAH develops because blood is forced to go through unusually narrowed blood vessels. Endothelin is a substance produced in the muscles that line the walls of the blood vessels and causes the muscles to contract, constricting the blood vessels and narrowing their diameter.

Endothelin receptor antagonists work by blocking the action of endothelin, allowing the vessels to relax and, subsequently, reducing blood pressure. These medications may slow PAH progression and ease its symptoms.

Research is underway to determine whether endothelin receptor antagonists can be used to treat Raynaud’s phenomenon. Like PAH, Raynaud’s is also a common complication of systemic scleroderma and involves blood vessel narrowing in the fingers and/or toes.

A review of several studies found that some endothelin receptor antagonists may be useful in relieving symptoms of Raynaud’s. But results of different studies are mixed, and further trials are necessary to confirm whether this class of medications can be effective in scleroderma patients with Raynaud’s phenomenon.

Types of endothelin receptor antagonists

Tracleer (bosentan), Letairis (ambrisentan), and Opsumit (macitentan) are three three endothelin receptor antagonists approved by the U.S. Food and Drug Administration (FDA) to treat PAH caused by scleroderma.

Side effects of endothelin receptor antagonists

Common side effects of endothelin receptor antagonists are changes in liver enzyme levels, raising a risk of liver injury; swelling of the limbs (edema); and low blood counts.

Endothelin receptor antagonists may also cause birth defects. Women taking these medications should consult with their prescribing physician before considering a pregnancy.

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