Macitentan:Dosage, Administration and Side Effect

Macitentan is an endothelin receptor antagonist used to treat pulmonary arterial hypertension (PAH) in adults. It works by blocking the effects of endothelin, a substance that can cause narrowing of blood vessels. By reducing this activity, macitentan can help reduce pulmonary vascular resistance and slow disease progression. Appropriate dosage and regular monitoring are important during treatment.

Recommended Dosage

The recommended dosage of macitentan for adults with PAH is 10 mg once daily. Doses higher than 10 mg once daily have not been adequately studied in patients with PAH and are not recommended. Macitentan is supplied as a 10 mg tablet for oral administration.

Patients should take macitentan exactly as prescribed. The tablet should be taken consistently according to the healthcare professional's instructions. Patients should not increase the dose or take additional tablets without medical advice.

Missed Dose

If a dose is missed, patients should follow the instructions provided by their healthcare professional or medication guide. Taking more than the prescribed amount to compensate for a missed dose is not recommended.

Patients who frequently forget doses should discuss the problem with their healthcare professional. Regular use is important for maintaining treatment of PAH.

Common Side Effects

Macitentan can cause side effects, although not every patient experiences them. Common adverse reactions include anemia, nasopharyngitis or pharyngitis, bronchitis, headache, influenza, and urinary tract infection.

Anemia is an important side effect because macitentan can decrease hemoglobin levels. Patients may experience tiredness, weakness, dizziness, or shortness of breath if anemia becomes significant.

Headache and respiratory infections may also occur during treatment. Patients should report persistent or severe symptoms to their healthcare professional.

Fluid Retention

Fluid retention is another important safety concern. Patients may develop swelling in the ankles, legs, or other areas of the body. Rapid weight gain or worsening swelling should be reported because fluid retention may require medical treatment.

Patients with symptoms of worsening heart or lung function may require additional evaluation to determine whether fluid retention is related to treatment or the underlying disease.

Liver Monitoring

Endothelin receptor antagonists can cause liver injury. Current prescribing information recommends obtaining baseline liver enzymes and monitoring liver function as clinically indicated.

Patients should inform their healthcare professional if they develop symptoms such as nausea, vomiting, abdominal discomfort, unusual tiredness, dark urine, or yellowing of the skin or eyes.

Pregnancy

Macitentan can cause fetal harm and is contraindicated during pregnancy. Females who can become pregnant should have a pregnancy test before starting treatment and should use effective contraception before treatment, during treatment, and for one month after stopping macitentan. If pregnancy occurs during treatment, macitentan should be discontinued as soon as possible under medical supervision.

Breastfeeding is also not recommended during treatment according to the current prescribing information.

Drug Interactions

Macitentan can interact with medicines that affect CYP3A4 and CYP2C9 enzymes. Strong CYP3A4 inducers and inhibitors can change macitentan exposure and should generally be avoided. Certain moderate dual or combined enzyme inhibitors may also increase drug exposure.

Patients should provide their healthcare professional with a complete list of prescription medicines, over-the-counter products, and supplements before starting treatment.