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Generic name: montelukast [ mon-te-LOO-kast ]
Brand name: Singulair
Dosage forms: oral granule, oral tablet, oral chewable tablet
Drug class: Leukotriene modifiers

Medically reviewed by Carmen Pope, BPharm. Last updated on Jul 20, 2022.

What is montelukast?

Montelukast helps to reduce inflammation and may be used to prevent asthma attacks in adults and children at least 2 years old.

Montelukast is also used to prevent exercise-induced bronchoconstriction (a narrowing of the air passages in the lungs due to exercise that is also known as exercise-induced asthma) in adults and children who are at least 6 years old.

For adults and children at least 2 years old with symptoms of seasonal or year-round (perennial) allergies, montelukast may be considered when other treatments have not worked.

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

Montelukast is not a fast-acting rescue medicine for asthma attacks and needs to be taken daily to work properly.

Montelukast was FDA approved in 1998.


Stop taking montelukast and call your doctor right away if you have any unusual changes in mood or behavior (such as agitation, confusion, depression, sleep problems, compulsive behaviors, hallucinations, or suicidal thoughts or actions).

Tell your doctor right away if you have signs of blood vessel inflammation: flu-like symptoms, severe sinus pain, a skin rash, numbness or a "pins and needles" feeling in your arms or legs.

Before taking this medicine

You should not use montelukast if you are allergic to it.

Tell your doctor if you have ever had:

  • mental illness or psychosis; or

  • asthma, or a history of severe allergic reaction (sneezing, runny or stuffy nose, wheezing, shortness of breath) after taking aspirin or another NSAID.

The chewable montelukast tablet may contain phenylalanine and could be harmful if you have phenylketonuria (PKU).

Tell your doctor if you are pregnant or breastfeeding.

Do not give this medicine to a child without a doctor's advice.

How should I take montelukast?

Take montelukast exactly as prescribed by your doctor and read all medication guides or instruction sheets about montelukast.

Montelukast is not a fast-acting rescue medicine for asthma attacks. Seek medical attention if your breathing problems get worse quickly, or if you think your medications are not working.

Montelukast is usually taken once every evening, with or without food.

For exercise-induced bronchoconstriction, take a single dose at least 2 hours before exercise, and do not take another dose for at least 24 hours.

Swallow the regular tablet whole, with a glass of water.

You must chew the chewable tablet before you swallow it.

Place the oral granules directly in your mouth and swallow, or mix them with applesauce, mashed carrots, rice, or ice cream. The granules may also be mixed with baby formula or breast milk. Do not use any other type of liquid. Use the mixture within 15 minutes. Do not save for later use.

If you also use an oral steroid medication, you should not stop using it suddenly when you start taking montelukast. Follow your doctor's instructions about tapering your dose.

Do not change your dose or stop using asthma medication without your doctor's advice.

Store montelukast at room temperature away from moisture and heat. Do not open a packet of montelukast oral granules until you are ready to use them.

What happens if I miss a dose of montelukast?

If you miss a dose of montelukast, skip the missed dose and use your next dose at the regular time. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking montelukast?

Avoid situations or activities that may trigger an asthma attack.

If your asthma symptoms get worse when you take aspirin, avoid taking aspirin or other NSAIDs (nonsteroidal anti-inflammatory drugs) such as ibuprofen (Advil, Motrin), naproxen (Aleve), celecoxib, diclofenac, indomethacin, meloxicam, and others.

Montelukast side effects

Get emergency medical help if you have signs of an allergic reaction to montelukast: hives, blisters, severe itching; difficult breathing; swelling of your face, lips, tongue, or throat.

Tell your doctor right away if you have signs of blood vessel inflammation: flu-like symptoms, severe sinus pain, a skin rash, numbness or a "pins and needles" feeling in your arms or legs.

Some people using montelukast have had new or worsening mental problems. Stop taking montelukast and call your doctor right away if you have unusual changes in mood or behavior, such as:

  • agitation, aggression, feeling restless or irritable;

  • anxiety, depression, confusion, problems with memory or attention;

  • stuttering, tremors, uncontrolled muscle movements;

  • suicidal thoughts or actions;

  • hallucinations, sleep problems, vivid, dreams, sleep-walking; or

  • compulsive or repetitive behaviors.

Common side effects of montelukast may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect montelukast?

Other drugs may affect montelukast, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all other medicines you use.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.