Home Drug Guide Macitentan

Drug Guide

Generic Name

Macitentan

Brand Names Opsumit

Classification

Therapeutic: Endothelin receptor antagonist for pulmonary arterial hypertension

Pharmacological: Selective endothelin receptor antagonist

FDA Approved Indications

Treatment of pulmonary arterial hypertension (PAH) to improve exercise ability and delay disease progression

Mechanism of Action

Macitentan blocks endothelin-1 from binding to its receptors (ET_A and ET_B), leading to vasodilation and inhibition of vascular remodeling in pulmonary arteries.

Dosage and Administration

Adult: 10 mg orally once daily; may adjust based on response and tolerability.

Pediatric: Not approved for pediatric use.

Geriatric: No specific dosage adjustment; monitor closely for adverse effects.

Renal Impairment: Use with caution; no specific dosage adjustment required.

Hepatic Impairment: Use is contraindicated in patients with significant hepatic impairment (Child-Pugh C).

Pharmacokinetics

Absorption: Well absorbed, bioavailability approximately 44%.

Distribution: Highly bound (>99%) to plasma proteins.

Metabolism: Metabolized primarily via CYP3A4 and CYP2C8 pathways.

Excretion: Excreted mainly via feces; minimal urinary excretion.

Half Life: About 16 hours, allowing once-daily dosing.

Contraindications

Pregnancy (category X) due to fetal risk.
Hypersensitivity to macitentan or excipients.

Precautions

Monitor liver function closely; hepatotoxicity risk.
Use with caution in patients on other medications affecting hepatic function or CYP450 enzymes.
Pregnant women must use contraception; pregnancy testing recommended before initiation.

Adverse Reactions - Common

Headache (Common)
Anemia (Common)
Flushing (Uncommon)

Adverse Reactions - Serious

Hepatotoxicity (Elevated liver enzymes or hepatitis) (Uncommon)
Fluid retention / edema (Uncommon)
Hypotension or syncope (Uncommon)

Drug-Drug Interactions

Potent CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin) may increase macitentan levels.
CYP3A4 inducers (e.g., rifampin) may decrease efficacy.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor for signs of hepatic impairment, anemia, and fluid retention.

Diagnoses:

Risk for hepatic injury
Impaired gas exchange related to pulmonary hypertension

Implementation: Administer once daily; monitor liver function tests and hemoglobin periodically.

Evaluation: Assess improvement in exercise capacity and symptom control; monitor for adverse effects.

Patient/Family Teaching

Take medication exactly as prescribed.
Report symptoms of hepatic dysfunction (jaundice, dark urine), excessive fatigue, or bleeding.
Avoid pregnancy during treatment and for at least one month after discontinuation.
Inform healthcare providers of all medications being taken.

Special Considerations

Black Box Warnings:

Pregnancy: risk of fetal harm; contraindicated in pregnant women.
Hepatotoxicity: monitor liver function closely.

Genetic Factors: No specific genetic testing required.

Lab Test Interference: Potential elevation in liver function tests.

Overdose Management

Signs/Symptoms: Hypotension, dizziness, headache.

Treatment: Supportive care; no specific antidote. Monitor vital signs and organ function.

Storage and Handling

Storage: Store at room temperature, 20-25°C (68-77°F).

Stability: Stable up to the expiration date on the package.