In the U.S.—

• Antiasthmatic, leukotriene receptor antagonist

Montelukast (mon-te-LOO-kast) is used in mild to moderate asthma to decrease the symptoms of asthma and the number of acute asthma attacks. However, this medicine should not be used to relieve an asthma attack that has already started.

This medicine is available only with your doctor's prescription, in the following dosage form:

Oral
• Tablets (U.S.)
• Chewable tablets (U.S.)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For montelukast, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to montelukast. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Montelukast has not been studied in pregnant women. However, it has been studied in animals and has not been found to cause birth defects or other problems.

Breast-feeding—It is not known whether montelukast passes into breast milk in humans. However, it does pass into breast milk in animals. Although most medicines pass into breast milk in small amounts, many of them may be used safely while breast-feeding. Mothers who are using this medicine and who wish to breast-feed should discuss this with their doctor.

Children—No information is available regarding use of montelukast in children younger than 6 years of age. The chewable tablet contains aspartame, which has phenylalanine as a component. Children who have phenylketonuria should be aware that each chewable tablet contains 0.842 mg of phenylalanine.

Older adults—Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults. There is no specific information comparing use of montelukast in the elderly with its use in other age groups. However, it has been used in some elderly patients and no differences in effectiveness or side effects were seen from those that occurred in younger adults.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your health care professional if you are taking or using any other prescription or nonprescription (over-the-counter [OTC]) medicine.

• Liver disease—Effects of montelukast may be increased because of slower removal from the body

Montelukast is used to prevent asthma attacks. It is not used to relieve an attack that has already started. For relief of an asthma attack that has already started, you should use another medicine. If you do not have another medicine to use for an attack or if you have any questions about this, check with your health care professional.

Dosing—

The dose of montelukast will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of montelukast. If your dose is different, do not change it unless your doctor tells you to do so.

The number of tablets that you take depends on the strength of the medicine.

• For asthma:
  • For tablets dosage form:
    • Adults and children 15 years of age and over—10 milligrams (mg) once a day in the evening.
  • For chewable tablets dosage form:
    • Children 6 to 15 years of age—5 mg once a day in the evening.
    • Children younger than 6 years of age—Use and dose must be determined by your doctor.

Missed dose—

If you miss a dose of this medicine, take it as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage—

To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

To work properly, montelukast must be taken every day at the same time, even if your asthma seems better.

Do not stop taking montelukast, even if your asthma seems better, unless you are told to do so by your doctor.

Check with your doctor if your symptoms do not improve or if your asthma gets worse.

You may be taking other medicines for asthma along with montelukast. Do not stop taking or reduce the dose of the other medicines, even if your asthma seems better, unless you are told to do so by your doctor.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if the following side effect occurs:

• Rare
  • Pus in the urine 
  
  

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

• More common
  • Headache 
  
  

• Less common
  • Abdominal or stomach pain;  cough;  dental pain;  dizziness;  fever;  heartburn;  skin rash;  stuffy nose;  weakness or unusual tiredness 
  
  

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.