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. Singulair is also used to prevent exercise-induced bronchoconstriction (narrowing of the air passages in the lungs) in adults and children who are at least 6 years old.

Singulair is also used to treat symptoms of year-round (perennial) allergies in adults and children who are at least 6 months old. It is also used to treat symptoms of seasonal allergies in adults and children who are at least 2 years old.

Singulair is used for allergies, only after other treatments have failed.

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

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

Singulair will not work fast enough to treat an asthma attack that has already begun. Use only a fast-acting inhalation medicine to treat an asthma attack. Talk with your doctor if any of your asthma medications do not seem to work as well in treating or preventing attacks.

Call your doctor right away if you feel that Singulair is not working as well as usual, or if it makes your condition worse. If it seems like you need to use more of any of your medications in a 24-hour period, talk with your doctor.

If you already take Singulair to prevent asthma or allergy symptoms, do not use it for exercise-induced bronchoconstriction.

It may take up to several weeks before your symptoms improve. Keep using Singulair as directed and tell your doctor if your symptoms do not improve after several weeks of treatment.

Take Singulair exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets.

Singulair is usually taken once daily in the evening for prevention of asthma or allergy symptoms. For exercise-induced bronchoconstriction, take a single dose at least 2 hours before you exercise, and do not take another dose for at least 24 hours. Follow your doctor's instructions.

Singulair is not a rescue medicine for asthma or bronchospasm attacks. Use only fast-acting inhalation medicine for an attack. Seek medical attention if your breathing problems get worse quickly, or if you think your medications are not working as well.

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

You must chew the Singulair chewable tablet before you swallow it.

The oral granules can be placed directly into the mouth and swallowed, or mixed with a spoonful of applesauce, mashed carrots, rice, or ice cream. Oral granules can also be mixed with 1 teaspoon of baby formula or breast milk. Do not use any other type of liquid for mixing the granules.

After opening or mixing the Singulair oral granules, you must use them within 15 minutes. Do not save an open packet or mixed medicine for later use.

It may take up to several weeks before your symptoms improve. Keep using the medication as directed and tell your doctor if your symptoms do not improve.

Use all asthma medications as directed. Your dose needs may change due to surgery, illness, stress, or a recent asthma attack. Do not change your dose or dosing schedule without your doctor's advice. Tell your doctor if any of your medicines seem to stop working.

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

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

Usual Adult Dose of Singulair for Allergic Rhinitis:

-10 mg orally once a day

Comments:
-For asthma, efficacy has been demonstrated when this drug was administered in the EVENING without regard to time of food ingestion.
-For allergic rhinitis, efficacy has been demonstrated for asthma when this drug was administered in the MORNING or EVENING without regard to time of food ingestion.
-Patients with both asthma and allergic rhinitis should take only one dose daily in the evening.

Uses:
-Prophylaxis and chronic treatment of asthma
-Relief of symptoms of seasonal allergic rhinitis and perennial allergic rhinitis

Usual Adult Dose of Singulair for Asthma -- Maintenance:

-10 mg orally once a day

Comments:
-For asthma, efficacy has been demonstrated when this drug was administered in the EVENING without regard to time of food ingestion.
-For allergic rhinitis, efficacy has been demonstrated for asthma when this drug was administered in the MORNING or EVENING without regard to time of food ingestion.
-Patients with both asthma and allergic rhinitis should take only one dose daily in the evening.

Uses:
-Prophylaxis and chronic treatment of asthma
-Relief of symptoms of seasonal allergic rhinitis and perennial allergic rhinitis

Usual Adult Dose for Bronchospasm Prophylaxis:

-10 mg orally once a day at least 2 hours before exercise

Comments:
-An additional dose should not be taken within 24 hours of a previous dose.
-Patients already taking this drug daily for another indication (including chronic asthma) should not take an additional dose to prevent EIB.
-A rescue short-acting beta-agonist should be available at all times.
-Daily administration for the chronic treatment of asthma has not been established to prevent acute episodes of EIB.

Use: Prevention of exercise-induced bronchoconstriction (EIB)

Usual Pediatric Dose of Singulair for Asthma -- Maintenance:

Less than 12 months: Not approved.

12 to 23 months:
-One sachet of 4 mg oral granules once a day

2 to 5 years:
-4 mg chewable tablet or one sachet oral granules once a day

6 to 14 years:
-5 mg chewable tablet orally once a day

15 years or older:
-10 mg tablet orally once a day

Comments:
-Doses should be taken in the evening.
-Efficacy has been demonstrated for asthma when this drug was administered in the evening without regard to time of food ingestion.

Use: Prophylaxis and chronic treatment of asthma in pediatric patients 12 months of age and older

Usual Pediatric Dose of Singulair for Allergic Rhinitis:

Seasonal Allergic Rhinitis:
Less than 2 years: Not approved.

2 to 5 years:
-4 mg chewable tablet or one sachet of 4 mg oral granules once a day

6 to 14 years:
-5 mg chewable tablet orally once a day

15 years or older:
-10 mg tablet orally once a day

Perennial Allergic Rhinitis:
Less than 6 months: Not approved.

6 to 23 months:
-One sachet of 4 mg oral granules once a day

2 to 5 years:
-4 mg chewable tablet orally once a day

6 to 14 years:
-5 mg chewable tablet orally once a day

15 years or older:
-10 mg tablet orally once a day

Comments:
-Efficacy has been demonstrated for asthma when this drug was administered in the MORNING or EVENING without regard to time of food ingestion.
-The time of administration may be individualized to suit patient needs.

Uses:
-Relief of symptoms of seasonal allergic rhinitis in patients 2 years of age and older
-Relief of symptoms of perennial allergic rhinitis in patients 6 months of age and older

Usual Pediatric Dose for Bronchospasm Prophylaxis:

Less than 6 years: Not approved.

6 to 14 years:
-5 mg chewable tablet orally once a day

15 years or older:
-10 mg tablet orally once a day

Comments:
-Dose should be taken at least 2 hours before exercise.
-An additional dose should not be taken within 24 hours of a previous dose.
-Patients already taking this drug daily for another indication (including chronic asthma) should not take an additional dose to prevent EIB.
-A rescue short-acting beta-agonist should be available at all times.
-Daily administration for the chronic treatment of asthma has not been established to prevent acute episodes of EIB.

Use: Prevention of exercise-induced bronchoconstriction (EIB) in patients 6 years of age and older

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

To make sure Singulair is safe for you, 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 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 Singulair to a child without a doctor's advice.

Skip the missed dose and use your next dose at the regular time. Do not use two doses at one time.

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

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.

Get emergency medical help if you have signs of an allergic reaction to Singulair: 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 Singulair have had new or worsening mental problems. Stop taking this medicine 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 Singulair side effects may include:

• stomach pain, diarrhea;

• fever or other flu symptoms;

• ear pain or full feeling, trouble hearing;

• headache; or

• cold symptoms such as runny or stuffy nose, sinus pain, cough, sore throat.

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.

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

Montelukast starts to lower leukotriene levels in your body right away, but it may take about a week before you notice the full benefits.

You can safely use this medicine for a long period of time. It will only work while you’re taking it.

Your dosage of Singulair will depend on your age and the formulation you take.

A typical dose for adults and adolescents 15 years or older is one, 10 milligram (mg) tablet a day. Children younger than 15 will require a lower dose.

Singulair is sometimes prescribed “off-label” to treat other medical conditions, such as hives or chronic obstructive pulmonary disorder (COPD).