The Food and Drug Administration on March 4 removed a warning pertaining to liver injury from the boxed warning on the ambrisentan label.
After a review of clinical trial data and postmarketing safety information, the FDA determined that ambrisentan (Letairis) presents only a small risk of liver injury and decided that monthly serum liver enzyme tests will no longer be required. The agency added that health care professionals should order liver enzyme tests if deemed clinically necessary. Ambrisentan is approved for the treatment of pulmonary arterial hypertension (PAH).
The boxed warning will continue to contain cautions about the use of ambrisentan during pregnancy. Preclinical studies showed that the drug can cause serious birth defects in animals. The drug will continue to be available only through a restricted distribution program called the Letairis Education and Access Program (LEAP).
In women of childbearing potential, the LEAP program requires evidence of a monthly pregnancy test before ambrisentan may be shipped.
Ambrisentan is an endothelin receptor antagonist. Endothelin is a naturally occurring substance that causes blood vessels to narrow, preventing normal blood flow in people with PAH. Ambrisentan has been shown to improve patients’ ability to exercise and to slow the progression of the disease.