ambrisentan 5 MG Oral Tablet [Letairis]

INDICATIONS AND USAGE Ambrisentan tablets are 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%). Ambrisentan is an endothelin receptor antagonist 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. Studies establishing effectiveness included trials predominantly in patients with WHO Functional Class II–III symptoms and etiologies of idiopathic or heritable PAH (60%) or PAH associated with connective tissue diseases (34%) ( 1 ).

DOSAGE AND ADMINISTRATION Initiate treatment at 5 mg once daily ( 2.1 ). May be started with tadalafil ( 2.1 ). Titrate at 4-week intervals as needed and tolerated ( 2.1 ). Do not split, crush, or chew tablets ( 2.1 ). 2.1 Adult Dosage Initiate treatment at 5 mg once daily, with or without tadalafil 20 mg once daily. At 4-week intervals, either the dose of ambrisentan or tadalafil can be increased, as needed and tolerated, to ambrisentan 10 mg or tadalafil 40 mg. Do not split, crush, or chew tablets. 2.2 Pregnancy Testing in Females of Reproductive Potential Exclude pregnancy before initiating treatment with ambrisentan in females of reproductive potential [see Warnings and Precautions ( 5.1 ), Use in Specific Populations ( 8.1 , 8.3 )].

WARNINGS AND PRECAUTIONS • Fluid retention may require intervention ( 5.2 ). • If patients develop acute pulmonary edema during initiation of therapy with ambrisentan tablets, consider underlying pulmonary veno-occlusive disease and discontinue treatment if necessary ( 5.3 ). • Decreases in sperm count have been observed in patients taking endothelin receptor antagonists ( 5.4 ). • Decreases in hemoglobin have been observed within the first few weeks; measure hemoglobin at initiation, at 1 month, and periodically thereafter ( 5.5 ). 5.1 Embryo-fetal Toxicity Based on data from animal reproduction studies, ambrisentan tablets may cause fetal harm when administered during pregnancy and are contraindicated during pregnancy. The available human data for endothelin receptor antagonists do not establish the presence or absence of major birth defects related to the use of ambrisentan tablets. Advise patients who can become pregnant of the potential risk to a fetus. Obtain a pregnancy test prior to initiation of treatment with ambrisentan tablets. Advise patients who can become pregnant to use effective contraception prior to initiation of treatment, during treatment, and for one month after discontinuation of treatment with ambrisentan tablets. When pregnancy is detected, discontinue use as soon as possible [see Dosage and Administration (2.2) , and Use in Specific Populations (8.1 , 8.3) ] . 5.2 Fluid Retention Peripheral edema is a known class effect of endothelin receptor antagonists, and is also a clinical consequence of PAH and worsening PAH. In the placebo-controlled studies, there was an increased incidence of peripheral edema in patients treated with doses of 5 or 10 mg ambrisentan tablets compared to placebo [see Adverse Reactions (6.1) ]. Most edema was mild to moderate in severity. In addition, there have been postmarketing reports of fluid retention in patients with pulmonary hypertension, occurring within weeks after starting ambrisentan tablets. Patients required intervention with a diuretic, fluid management, or, in some cases, hospitalization for decompensating heart failure. If clinically significant fluid retention develops, with or without associated weight gain, further evaluation should be undertaken to determine the cause, such as ambrisentan tablets or underlying heart failure, and the possible need for specific treatment or discontinuation of ambrisentan tablets therapy. 5.3 Pulmonary Edema with Pulmonary Veno-occlusive Disease (PVOD) If patients develop acute pulmonary edema during initiation of therapy with vasodilating agents such as ambrisentan tablets, the possibility of PVOD should be considered, and if confirmed ambrisentan tablets should be discontinued. 5.4 Decreased Sperm Counts Decreased sperm counts have been observed in human and animal studies with another endothelin receptor antagonist and in animal fertility studies with ambrisentan. Ambrisentan tablets may have an adverse effect on spermatogenesis [see Use in Specific Populations (8.6) and Nonclinical Toxicology (13.1) ]. 5.5 Hematological Changes Decreases in hemoglobin concentration and hematocrit have followed administration of other endothelin receptor antagonists and were observed in clinical studies with ambrisentan tablets. These decreases were observed within the first few weeks of treatment with ambrisentan tablets, and stabilized thereafter. The mean decrease in hemoglobin from baseline to end of treatment for those patients receiving ambrisentan tablets in the 12-week placebo-controlled studies was 0.8 g/dL. Marked decreases in hemoglobin (> 15% decrease from baseline resulting in a value below the lower limit of normal) were observed in 7% of all patients receiving ambrisentan tablets (and 10% of patients receiving 10 mg) compared to 4% of patients receiving placebo. The cause of the decrease in hemoglobin is unknown, but it does not appear to result from hemorrhage or hemolysis. In the long-term open-label extension of the two pivotal clinical studies, mean decreases from baseline (ranging from 0.9 to 1.2 g/dL) in hemoglobin concentrations persisted for up to 4 years of treatment. There have been postmarketing reports of decreases in hemoglobin concentration and hematocrit that have resulted in anemia requiring transfusion. Measure hemoglobin prior to initiation of ambrisentan tablets, at one month, and periodically thereafter. Initiation of ambrisentan tablets therapy is not recommended for patients with clinically significant anemia. If a clinically significant decrease in hemoglobin is observed and other causes have been excluded, consider discontinuing ambrisentan tablets.

CONTRAINDICATIONS Pregnancy ( 4.1 ) Idiopathic Pulmonary Fibrosis ( 4.2 ) 4.1 Pregnancy Ambrisentan tablets may cause fetal harm when administered to a pregnant female. Ambrisentan tablets are contraindicated in females who are pregnant. Ambrisentan tablets were consistently shown to have teratogenic effects when administered to animals. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus [see Dosage and Administration ( 2.2 ), Warnings and Precautions ( 5.1 ), and Use in Specific Populations ( 8.1 )] . 4.2 Idiopathic Pulmonary Fibrosis Ambrisentan tablets are contraindicated in patients with Idiopathic Pulmonary Fibrosis (IPF), including IPF patients with pulmonary hypertension (WHO Group 3) [see Clinical Studies ( 14.4 )] .

Mechanism of Action Endothelin-1 (ET-1) is a potent autocrine and paracrine peptide. Two receptor subtypes, ET A and ET B , mediate the effects of ET-1 in the vascular smooth muscle and endothelium. The primary actions of ET A are vasoconstriction and cell proliferation, while the predominant actions of ET B 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 (K i = 0.011 nM) ET A receptor antagonist with a high selectivity for the ET A versus ET B receptor (> 4000-fold). The clinical impact of high selectivity for ET A is not known.