Montelukast

Leukotriene receptor antagonist · also known as Singulair

Cysteinyl leukotriene receptor antagonist; blocks a mast cell mediator class that antihistamines do not address.

How it relates to mast cells: Downstream of the mast cell
Types of studies cited: Randomised controlled trial
Approved in the US for: asthma, exercise-induced bronchoconstriction, allergic rhinitis
Randomised trials in: chronic urticaria
Also covers: Zafirlukast (Accolate), Pranlukast

What this relationship means: Acts after mast-cell mediators are released rather than stabilising the mast cell itself. This includes treatments that block mediator receptors, degrade a mediator, or oppose the physiology of an acute reaction. It describes where the intervention acts, not its clinical importance. A 2025 practical-management review places this at step 3 of the sequence it describes — the next class described; in Canada montelukast is the only available option. That is what the review reports, not a recommendation from this site.

Mechanism of action

Montelukast antagonises the cysteinyl leukotriene receptor CysLT1. Cysteinyl leukotrienes are lipid mediators synthesised by mast cells on activation rather than stored preformed in granules, and they act on bronchial smooth muscle, vascular permeability, and mucus secretion.

Leukotrienes are released by the same cell as histamine but act at separate receptors, so H1 antagonism does not block this pathway. That distinction is the mechanistic reason leukotriene antagonists appear in mast cell disease management reviews. The controlled outcome citation on this page concerns chronic urticaria rather than MCAS.

Sources

Efficacy of leukotriene receptor antagonist in chronic urticaria Peer-reviewed study 2001 PMID 11678862 · link checked 21 Aug 2026
Montelukast sodium US prescribing information Drug label · link checked 21 Aug 2026
Leukotriene Receptor Antagonists Reference work 2012 PMID 31644022 · link checked 20 Aug 2026
Mast Cell Activation Syndrome and Mastocytosis: Initial Treatment Options and Long-Term Management Review article 2019 PMID 30961835 · link checked 20 Aug 2026

What this evidence cannot establish

No controlled evidence in MCAS. The randomised comparison was in a selected chronic-urticaria population, while the MCAS bridge rests on downstream mediator pharmacology and management reviews rather than trials in this population. Montelukast also carries a US boxed warning for serious neuropsychiatric events; that is a labelled safety fact, not an evidence-strength judgment.

What this page does not say

No dosing, and no claim that this works. The entry describes a published mechanism, the cited study types, and what those studies cannot establish — nothing further. Why the site is built this way.

Recently verified. Verified 21 Aug 2026