Macitentan (Opsumit) is a new drug approved for the treatment of pulmonary arterial hypertension. It's intended to delay disease progression and diminish the likelihood of hospitalization for pulmonary arterial hypertension. Macitentan is an endothelin-receptor blocker that relaxes the pulmonary arteries. Endothelin-1 and its receptors play active participants in several disease processes, including vasoconstriction, fibrosis, proliferation, hypertrophy, and inflammation. In pulmonary arterial hypertension, endothelin is overexpressed-its action on its receptors is excessive-producing vascular hypertrophy and organ damage. By blocking the receptors, macitentan prevents these negative effects. The drug is taken orally daily.

Macitentan is a pregnancy category X drug. Like other drugs in the same class, macitentan's label carries a boxed warning that the drug shouldn't be used by pregnant women because it can harm the developing fetus. Consequently, only prescribers enrolled in the Opsumit Risk Evaluation and Mitigation Strategy (REMS)-a special program that limits who can prescribe, distribute, and take the drug-can prescribe macitentan to female patients, who must also enroll in the REMS. (Men do not participate in the REMS.) Because other drugs in the same class can cause hepatotoxicity and liver failure, the drug's labeling carries a warning that it, too, could do so. However, the most common adverse effects of macitentan are anemia, nasopharyngitis, sore throat, bronchitis, headache, flu, and urinary tract infections.

Nurses prescribing macitentan or caring for female patients taking the drug should confirm that they aren't pregnant before they begin macitentan therapy. Nurses should impress upon women the importance of using a method of birth control that's considered highly effective (such as an intrauterine device, a contraceptive implant, or tubal sterilization) during treatment with macitentan. Alternatively, the woman may also use a combination of methods (such as a hormone method with a barrier method or two barrier methods). Even if her partner has had a vasectomy, a hormone or barrier method must also be used. The drug's labeling contains complete information on acceptable birth control alternatives: http://1.usa.gov/1cYAkbF.

With all patients, nurses should confirm that baseline liver enzyme levels were determined prior to the start of drug therapy. Macitentan is dispensed with a medication guide containing important information for patients regarding the drug and its adverse effects. Nurses should instruct patients to read the medication guide every time they fill a prescription because it will contain the most current information about safety and adverse effects.

To read the FDA news release regarding the approval, go to http://1.usa.gov/18mwHtr.