Ambrisentan (2 brand names, 1 dosage form, 1 route)
Available dosage forms: TABLET.
Routes of administration: ORAL.
Brand Names
- AMBRISENTAN
- LETAIRIS
Boxed Warning
Letairis is contraindicated for use during pregnancy because it may cause major birth defects if used by pregnant patients, based on studies in animals [see Contraindications (4.1), Warnings and Precautions (5.1), and Use in Specific Populations (8.1)]. Therefore, for females of reproductive potential, exclude pregnancy before the initiation of treatment with Letairis. Advise use of effective contraception before initiation, during treatment, and for one month after treatment with Letairis [see Dosage and Administration (2.2) Contraindications (4.1), Warnings and Precautions (5.1), and Use in Specific Populations (8.1, 8.3)]. When pregnancy is detected, discontinue Letairis as soon as possible (5.1).
Indications and Usage
Letairis is indicated for the treatment of pulmonary arterial hypertension (PAH) (WHO Group 1) in adult patients: To improve exercise ability and delay clinical worsening. In combination with tadalafil to reduce the risks of disease progression and hospitalization for worsening PAH, and to improve exercise ability [see Clinical Studies (14.2)]. Studies establishing effectiveness included predominantly patients with WHO Functional Class II–III symptoms and etiologies of idiopathic or heritable PAH (60%) or PAH associated with connective tissue diseases (34%).
Adverse Reactions
Clinically significant adverse reactions that appear in other sections of the labeling include: Embryo-fetal Toxicity [see Warnings and Precautions (5.1), Use in Specific Populations (8.1)] Fluid Retention [see Warnings and Precautions (5.2)] Pulmonary Edema with PVOD [see Warnings and Precautions (5.3)] Decreased Sperm Count [see Warnings and Precautions (5.4)] Hematologic Changes [see Warnings and Precautions (5.5)]
Drug Interactions
Multiple dose coadministration of ambrisentan and cyclosporine resulted in an approximately 2-fold increase in ambrisentan exposure in healthy volunteers; therefore, limit the dose of ambrisentan to 5 mg once daily when coadministered with cyclosporine [see Clinical Pharmacology (12.3)].
Mechanism of Action
Endothelin-1 (ET-1) is a potent autocrine and paracrine peptide. Two receptor subtypes, ETA and ETB, mediate the effects of ET-1 in the vascular smooth muscle and endothelium. The primary actions of ETA are vasoconstriction and cell proliferation, while the predominant actions of ETB are vasodilation, antiproliferation, and ET-1 clearance. In patients with PAH, plasma ET-1 concentrations are increased as much as 10-fold and correlate with increased mean right atrial pressure and disease severity. ET-1 and ET-1 mRNA concentrations are increased as much as 9-fold in the lung tissue of patients with PAH, primarily in the endothelium of pulmonary arteries. These findings suggest that ET-1 may play a critical role in the pathogenesis and progression of PAH. Ambrisentan is a high-affinity (Ki=0.011 nM) ETA receptor antagonist with a high selectivity for the ETA versus ETB receptor (>4000-fold). The clinical impact of high selectivity for ETA is not known.
Overdosage
There is no experience with overdosage of Letairis. The highest single dose of Letairis administered to healthy volunteers was 100 mg, and the highest daily dose administered to patients with PAH was 10 mg once daily. In healthy volunteers, single doses of 50 mg and 100 mg (5 to 10 times the maximum recommended dose) were associated with headache, flushing, dizziness, nausea, and nasal congestion. Massive overdosage could potentially result in hypotension that may require intervention.