Drug Name

Singulair (Montelukast)

 Drug Uses

Montelukast is used for the treatment of asthma and seasonal allergic rhinitis. Montelukast begins working after 3 to 14 days of therapy. Therefore, it should not be used for the treatment of an acute asthmatic attack.

The recommended dose of montelukast is 4, 5, or 10 mg daily. The 4 and 5 mg tablets are used in children. Montelukast should be taken in the evening with or without food.

 Drug Class and Mechanism

Montelukast is an oral leukotriene receptor antagonist for the treatment of asthma and seasonal allergic rhinitis (hay fever). Leukotrienes are a group of naturally occurring chemicals in the body that promote inflammation in asthma and seasonal allergic rhinitis and in other diseases in which inflammation is important (such as allergy). They are formed by cells, released, and then bound to other cells, and it is the binding to these other cells that stimulates the cells to promote inflammation. Montelukast works in a manner similar to zafirlukast (Accolate), blocking the binding of some leukotrienes. Unlike zafirlukast, montelukast does not inhibit CYP2C9 or CYP3A4, two enzymes in the liver that are important in breaking down and eliminating many drugs. Therefore, unlike zafirlukast, montelukast is not expected to affect the elimination of other drugs. The safety and effectiveness of montelukast has been demonstrated in children as young as 6 months of age. It was approved by the FDA in 1998.

Take the missed dose as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and take the next regularly scheduled dose as directed. Do not take a double dose of this medication.

Tablets should be stored at room temperature, 15-30 degrees C (59-86 degrees F).

 Warnings/Precautions

Avoid items or activities that may trigger an asthma attack. Phenobarbital increases the blood concentration of montelukast by about 40%. Rifampin may have the same effect. Therefore, the dose of montelukast may need to be reduced when given concurrently with these drugs. Montelukast crosses the placenta into the fetus following oral administration to animals, but there have been no adequate studies in pregnant women to determine the effects on the fetus. Physicians may prescribe zafirlukast during pregnancy if it is felt that its benefits outweigh the potential but unknown risks to the fetus. Studies in animals have shown that montelukast is excreted in milk; however, it is not known if montelukast is secreted into breast milk in humans.

 Possible Side Effects

The most common side effects with montelukast are headache, dizziness, abdominal pain, sore throat, and rhinitis (inflammation of the inner lining of the nose). These side effects occur in 1 in 50 to 1 in 7 persons who take montelukast.

 More Information

• If you experience any of the following serious side effects, stop taking montelukast and seek emergency medical attention or notify your doctor immediately:
  • an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);
  • numbness, tingling, or pain;
  • a rash or unexplained open sores or bruising;
  • a flu-like illness;
  • severe inflammation (pain and swelling) of the sinuses; or
  • worsening respiratory symptoms.
• Other, less serious side effects may be more likely to occur. Continue to take montelukast and talk to your doctor if you experience
  • upset stomach, stomach pain, or heartburn;
  • dizziness or headache;
  • tiredness;
  • sore throat or cough, or
  • nasal irritation.
• Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.