montelukast
Montelukast (Singulair) is an oral medicine that blocks leukotrienes, inflammatory chemicals that tighten airways and trigger allergy symptoms. It is used for the prevention and long-term treatment of asthma, prevention of exercise-induced bronchoconstriction, and relief of seasonal and perennial allergic rhinitis.
This page is based on FDA prescribing information for montelukast sodium tablets, cross-checked with DailyMed labeling, MedlinePlus, and the National Cancer Institute drug dictionary; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
Leukotrienes are chemical alarm signals released during allergic reactions that tell the airways to tighten and swell. Montelukast acts like a plug in the receptor that receives those signals, so the alarm never gets through and the airways stay calmer.
In simple terms
Montelukast blocks a receptor called CysLT1 that is found on cells in the airways and throughout the body. When the body releases inflammatory chemicals called leukotrienes — especially during allergic reactions or asthma flare-ups — they bind to this receptor and cause the airway muscles to tighten, the lining to swell, and mucus to increase. By blocking the receptor, montelukast prevents these effects, helping to keep airways open and reducing allergy symptoms such as sneezing, nasal congestion, and runny nose. It is taken by mouth once daily for long-term prevention and is not used to treat sudden breathing problems.
In depth
Montelukast is a selective, orally bioavailable antagonist of the cysteinyl leukotriene 1 (CysLT1) receptor. CysLT1 is a G protein-coupled receptor expressed on airway smooth muscle cells, macrophages, eosinophils, mast cells, and other inflammatory cells. The cysteinyl leukotrienes LTD4, LTC4, and LTE4 are potent inflammatory mediators derived from arachidonic acid via the 5-lipoxygenase pathway; they bind CysLT1 to produce bronchoconstriction, increased vascular permeability, mucus hypersecretion, eosinophil recruitment, and airway edema. By competitively blocking CysLT1, montelukast inhibits these leukotriene-mediated inflammatory events, including bronchoconstriction, leukocyte migration, and increased capillary permeability. Montelukast is used for prophylaxis and chronic treatment of asthma, prevention of exercise-induced bronchoconstriction, and relief of seasonal and perennial allergic rhinitis symptoms.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
How montelukast plugs the leukotriene alarm
- Leukotrienes are chemical alarm signals released during allergic reactions that tell the airways to tighten and swell.
- Montelukast blocks a receptor called CysLT1 that is found on cells in the airways and throughout the body.
- When the body releases inflammatory chemicals called leukotrienes — especially during allergic reactions or asthma flare-ups — they bind to this receptor and cause the airway muscles to tighten, the lining to swell, and mucus to increase.
- Montelukast acts like a plug in the receptor that receives those signals, so the alarm never gets through and the airways stay calmer.
Target: Cysteinyl leukotriene 1 receptor (CysLT1)
A G protein-coupled receptor found on airway smooth muscle cells, eosinophils, mast cells, and other inflammatory cells; when activated by leukotrienes D4, C4, and E4 it drives bronchoconstriction, mucus secretion, and inflammatory cell recruitment. Montelukast blocks this receptor.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in United States
FDA- Prophylaxis and chronic treatment of asthma in adults and adolescent patients 15 years of age and older.
- Prevention of exercise-induced bronchoconstriction in patients 15 years of age and older.
- Relief of symptoms of seasonal allergic rhinitis in patients 15 years of age and older, and perennial allergic rhinitis in patients 15 years of age and older; reserve use for patients who have an inadequate response or intolerance to alternative therapies.
Approved uses in United States
DailyMed- Prophylaxis and chronic treatment of asthma in adults and pediatric patients 12 months of age and older.
- Prevention of exercise-induced bronchoconstriction in patients 6 years of age and older.
- Relief of symptoms of seasonal allergic rhinitis in patients 2 years of age and older and perennial allergic rhinitis in patients 6 months of age and older; reserve use for patients who have an inadequate response or intolerance to alternative therapies.
Official sources
The statements on this page trace back to these records.
- U.S. Food and Drug Administration: montelukast prescribing information
U.S. Food and Drug Administration
- DailyMed: MONTELUKAST SODIUM labeling
DailyMed, U.S. National Library of Medicine
- MedlinePlus: montelukast
MedlinePlus, U.S. National Library of Medicine
- National Cancer Institute: montelukast sodium
National Cancer Institute
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.