Letairis® (ambrisentan) is a prescription medicine to treat pulmonary arterial hypertension (PAH) (WHO Group 1) in patients with WHO Class II or III symptoms. PAH is high blood pressure in the arteries of the lungs. Letairis can improve your ability to exercise, and it can help slow down the worsening of your physical condition and symptoms.

Letairis Side Effects

What are the possible side effects of Letairis?

   Serious side effects of Letairis include:

  • Serious birth defects. (See “What is the most important information I should know about Letairis?”)
  • Swelling all over the body (fluid retention) can happen within weeks after starting Letairis. Tell your doctor right away if you have any unusual weight gain, tiredness, or trouble breathing while taking Letairis. These may be symptoms of a serious health problem. You may need to be treated with medicine or need to go to the hospital.
  • Sperm count reduction. Reduced sperm counts have been observed in some men taking a drug similar to Letairis, an effect which might impair their ability to father a child. Tell your doctor if remaining fertile is important to you.
  • Low red blood cell levels (anemia) can happen during the first weeks after starting Letairis. If this happens, you may need a blood transfusion. Your doctor will do blood tests to check your red blood cells before starting Letairis. Your doctor may also do these tests during treatment with Letairis.

The most common side effects of Letairis are:

  • Swelling of hands, legs, ankles and feet (peripheral edema)
  • Stuffy nose (nasal congestion)
  • Inflamed nasal passages (sinusitis)
  • Hot flashes or getting red in the face (flushing)

Some medicines that are like Letairis can cause liver problems. Tell your doctor if you get any of these symptoms of a liver problem while taking Letairis:

  • loss of appetite
  • nausea or vomiting
  • fever
  • achiness
  • generally do not feel well
  • pain in the upper right stomach (abdominal) area
  • yellowing of your skin or the whites of your eyes
  • dark urine
  • itching

These are not all of the possible side effects of Letairis. Tell your doctor if you have any side effect that bothers you or that does not go away. For more information, ask your doctor or pharmacist.

Call your doctor for medical advice about side effects. You may report side effects to FDA at

Please see full Prescribing Information, including Medication Guide, with Important warnings.

If you have questions or concerns regarding your treatment options, call 1-866-664-5327 or visit www.gilead.com for more information.