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U.S. Department of Health and Human Services


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Letairis (ambrisentan) Tablets

Detailed View: Safety Labeling Changes Approved By FDA Center for Drug Evaluation and Research (CDER) – August 2013

Summary View



  • Letairis was consistently shown to have teratogenic effects when administered to animals.


  • Embryo-fetal Toxicity - Letairis may cause fetal harm when administered during pregnancy and is contraindicated for use in females who are pregnant…
  • Letairis REMS Program - Letairis REMS, because of the risk of embryo-fetal toxicity…
Decreased Sperm Count
  • Decreased sperm counts have been observed in human and animal studies with another endothelin receptor antagonist and in animal fertility studies with Ambrisentan. Letairis may have an adverse effect on spermatogenesis. Counsel patients about potential effects on fertility.


Clinically significant adverse reactions that appear in other sections of the labeling include:
  • Embryo-fetal toxicity
  • Fluid Retention
  • Pulmonary Edema with PVOD
  • Decreased Sperm Count
  • Hematologic changes


  • Risk Summary - Letairis may cause fetal harm when administered to a pregnant woman and is contraindicated during pregnancy…
  • Animal Data - Letairis was teratogenic at oral doses of ≥ 15 mg/kg/day (AUC 51.7 h•μg/ml) in rats and ≥ 7 mg/kg/day (24.7 h•μg/ml) in rabbits…
Nursing Mothers
  • It is not known whether ambrisentan is present in human milk…
Females and Males of Reproductive Potential
  • Pregnancy Testing - Female patients of reproductive potential must have a negative pregnancy test prior to initiation of treatment, monthly pregnancy test during treatment, and 1 month after stopping treatment with Letairis...
  • Contraception - Female patients of reproductive potential must use acceptable methods of contraception during treatment with Letairis and for 1 month after stopping treatment with Letairis…
  • Infertility – Males - In a 6-month study of another endothelin receptor antagonist, bosentan, 25 male patients with WHO functional class III and IV PAH and normal baseline sperm count were evaluated for effects on testicular function…


What is the most important information I should know about Letairis?
  • WomenFemales must not be pregnant when they start taking LETAIRISLetairis or become pregnant during treatment with Letairis…
  • Females who are able to get pregnant must use two acceptable forms of birth control, during treatment with Letairis, and for one month after stopping Letairis because the medicine may still be in the body…
What is Letairis?
  • It is not known if Letairis is safe and effective in children.
What should I avoid while taking Letairis?
  • It is not known if Letairis passes into your breast milk. You should not breastfeed if you are taking Letairis. Talk to your doctor about the best way to feed your baby if you take Letairis.
What are the possible side effects of Letairis?
  • Letairis can cause serious side effects including…
How should I store Letairis?
  • Store Letairis at room temperature between 68°F to 77° F (20°C to 25°C), in the package it comes in.


Detailed View: Safety Labeling Changes Approved By FDA Center for Drug Evaluation and Research (CDER) -- February 2008


The detailed view includes drug products with safety labeling changes to the BOXED WARNING, CONTRAINDICATIONS, WARNINGS, PRECAUTIONS, ADVERSE REACTIONS, or PATIENT PACKAGE INSERT/MEDICATION GUIDE sections. Deletions or editorial revisions made to these sections are not included in this summary.


Summary View


Sections ModifiedSummary of Changes to Contraindications and Warnings


  • Fluid Retention


  • Postmarketing Experience
    • Fluid Retention


  • The most common side effects of Letairis
    • Swelling of hands, legs, ankles and feet (peripheral edema)...


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 Letairis compared to placebo [see Adverse Reactions (6)]. Most edema was mild to moderate in severity, and it occurred with greater frequency and severity in elderly patients...