Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor immediately if any of these rare but serious side effects occur: mental/mood changes (such as agitation, aggression, anxiety, trouble sleeping, abnormal dreams, sleep-walking, memory/attention problems, depression, hallucinations, thoughts of harming yourself/suicide), numbness/tingling/shooting pain in the arms or legs, sinus pain/swelling, muscle weakness. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

Montelukast is used regularly to prevent the wheezing and shortness of breath caused by asthma and decrease the number of asthma attacks. Montelukast is also used before exercise to prevent breathing problems during exercise (bronchospasm). This medication can help decrease the number of times you need to use your rescue inhaler. This medication is also used to relieve symptoms of hay fever and allergic rhinitis (such as sneezing, stuffy/runny/itchy nose).This medication does not work immediately and should not be used to treat sudden asthma attacks or other breathing problems.This drug works by blocking certain natural substances (leukotrienes) that may cause or worsen asthma and allergies. It helps make breathing easier by reducing swelling (inflammation) in the airways. Remember to always take Singulair at night.