What Is Montelukast Sodium?

Montelukast sodium (Singulair) is a drug used for long-term prevention of asthma in adults and children aged 2 and older. Physicians also prescribe montelukast to relieve allergy symptoms, such as a runny nose, nasal congestion and sneezing.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.


Montelukast sodium blocks immune system components called leukotrienes that cause inflammation in the respiratory tract. Decreasing inflammation reduces swelling that narrows airways. Montelukast also relaxes bronchial tube walls.


Montelukast is available in tablets, chewable tablets and granules. Take montelukast sodium every day, as prescribed, even if you are not experiencing symptoms. Montelukast does not treat an asthma attack.

Side Effects

Many side effects are associated with montelukast, although they are not common. Side effects can include headaches, abdominal pain, abnormal dreams, drowsiness, heartburn, infections, insomnia, muscle aches and nausea.


Rare but serious side effects call for medical attention. These include an allergic reaction, hallucinations, depression and a worsening of asthma or allergy symptoms.


Patients with liver disease may not be able to safely use montelukast because it can lead to liver damage, although the incidence is rare. People with phenylketonuria cannot take the chewable tablets because they contain phenylalanine.