Singulair (Montelukast) Side Effects, Important Information, Before Taking & More

Singulair is a drug used to prevent shortness of breath and wheezing due to asthma attacks. It is particularly helpful in reducing the frequency of asthma attacks. Singulair is also used to relieve symptoms of allergic rhinitis, hay fever, and other allergies that can cause itchy, stuffy or a runny nose and sneezing. It is also helpful in preventing exercise-induced asthma. Singulair works by blocking natural substances known as leukotriene in the body that may cause or aggravate allergies and asthma.


Side effects

Use of Singulair does not produce any serious side effects in most people. However, if you experience the following common side effects and they do not go away with time, then consult your doctor:

  • Toothache
  • Fever, hoarseness, sore throat, cough, stuffy nose
  • Headache
  • Dizziness
  • Ear infection or an earache
  • Feeling tired
  • Upper respiratory infection
  • Mild rash


Go to emergency if you have any of the following rare but serious side effects:

  • Tremors or shaking
  • Skin rash, muscle weakness, pain, severe tingling, and numbness
  • Severe sinus pain, irritation, or swelling
  • Easy bruising, red or purple spots under the skin, unusual breathing
  • Mood or behavior changes, suicidal thoughts, depression, anxiety
  • Abnormal dreams
  • Uncontrolled muscle movement
  • Depression
  • Memory or attention problems
  • Worsening asthma symptoms


Although an allergic reaction to Singulair is rare, consult your doctor if you have:

  • Severe dizziness
  • Hives or rash
  • Itching or swelling of the face
  • Trouble breathing

How to use Singulair

Read the medical information leaflet about Singulair before you start taking it. If you are taking chewable Singulair tablets, chew them properly before swallowing them completely. Regular Singulair tablets can be taken by mouth, with water, with or without food. The dosage varies according to an individual’s response to treatment and condition.

Leukotriene is a chemical that is released by the body in instances where you breathe in allergen like pollen. They can cause swelling in your lungs and contraction in the muscles around the airways that can result in asthma symptoms. If you are taking Singulair for asthma or for asthma and allergies both it is better to take your dose in the evening, but if you are taking it only to prevent allergies, then you can take Singulair either in the morning or evening. Schedule a time and take Singulair at the same time daily.


If you are taking Singulair to prevent exercise-induced breathing problems, then take this medicine at least a couple of hours before you exercise. Take one dose daily but if you are already using Singulair daily for allergies or asthma then do not take a dose before exercise.

Do not change dosage without your doctor’s consultation. Keep using Singulair to keep your asthma under control even during acute asthma attacks or on days when you have no asthma symptoms. It takes time for Singulair to work and is not used to treat acute attacks of asthma. Therefore, during an asthma attack or when experiencing other breathing problems, use your prescribed quick-relief inhaler. If your quick-relief inhaler is unable to help or if allergy symptoms and breathing problems persist contact your doctor.



Avoid using Singulair, if you are allergic to montelukast. Before taking Singulair; inform your doctor if you have a medical history of liver disease. The chewable tablets of Singulair may contain aspartame which may not be safe for people who have phenylketonuria (PKU). Find out about the safety of Singulair in such cases before using it. Nursing and pregnant women should take Singulair after discussing it with their doctor.