Side Effects of Singulair

Singulair is a leukotriene (loo-koe-TRY-een) inhibitor. Leukotrienes are chemicals your body releases when you breathe in an allergen (such as pollen). These chemicals cause swelling in your lungs and tightening of the muscles around your airways, which can result in asthma symptoms.

Singulair is used to prevent asthma attacks in adults and children as young as 12 months old. It is also used to relieve runny nose and sneezing caused by allergies in adults and children as young as 6 months old.

Do not give Singulair to a child without a doctor’s advice.

Singulair is also used to prevent exercise-induced bronchoconstriction (narrowing of the air passages in the lungs) in adults and teenagers who are at least 15 years old and are not already taking this medicine for other conditions.

If you already take Singulair to prevent asthma or allergy symptoms, do not use an extra dose to treat exercise-induced bronchoconstriction.

Get emergency medical help if you have any of these signs of an allergic reaction to Singulair: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Call your doctor at once if you have any of these serious side effects:

  • skin rash, bruising, severe tingling, numbness, pain, muscle weakness;
  • mood or behavior changes, anxiety, depression, or thoughts about suicide or hurting yourself;
  • tremors or shaking;
  • easy bruising, unusual bleeding (nose, mouth, vagina, or rectum), purple or red pinpoint spots under your skin;
  • severe sinus pain, swelling, or irritation; or
  • worsening asthma symptoms.

Less serious Singulair side effects may include:

  • headache;
  • stomach pain, heartburn, upset stomach, nausea, diarrhea;
  • tooth pain;
  • tired feeling;
  • fever, stuffy nose, sore throat, cough, hoarseness; or
  • mild rash.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

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