Angiotensin 2 receptor antagonists or blockers are a group of medications that help dilate blood vessels to lower blood pressure. They are used for treating high blood pressure, heart failure, and Raynaud’s phenomenon, a common symptom of scleroderma.
How angiotensin 2 receptor antagonists work
Patients with Raynaud’s phenomenon experience recurrent episodes in which their fingers and/or toes turn white, blue, and red in response to cold temperatures or emotional stress. These symptoms happen because the blood vessels suddenly spasm (narrow), blocking blood flow to the affected areas.
The narrowing of the blood vessels can be caused by certain chemicals present in the blood. One such chemical is known as angiotensin 2, whose circulating levels are unusually high in people with systemic scleroderma. Angiotensin 2 binds to the angiotensin 2 receptors located on the muscular walls of blood vessels, causing the vessels to constrict.
Angiotensin 2 receptor antagonists work by preventing angiotensin 2 from binding to its receptor, allowing blood vessels to expand. An angiotensin 2 receptor antagonist known as losartan (marketed as Cozaar, manufactured by Merck) is commonly used as an alternative to calcium channel blockers in treating Raynaud’s phenomenon.
Studies on angiotensin 2 receptor antagonists
Only one randomized controlled trial compared the effects of an angiotensin 2 receptor antagonist with that of a calcium channel blocker in patients who had isolated Raynaud’s or Raynaud’s with systemic scleroderma. Patients received either 50 mg of losartan or 40 mg of nifedipine (a calcium channel blocker) daily for three months. The results showed that losartan was more effective in reducing the severity and frequency of Raynaud’s attacks compared to nifedipine, and researchers recommended a longer trial in systemic scleroderma patients with Raynaud’s.
Further details
Some side effects of angiotensin 2 receptor antagonists include dizziness, localized tissue swelling, and increased levels of potassium in the blood (hyperkalemia).
Angiotensin 2 receptor antagonists are harmful to a developing fetus. Women who take angiotensin 2 receptor antagonists and are planning to become pregnant should discuss this with their treating physician.
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