Montelukast (Singulair) Not Effective in Controlling Allergic Symptoms Outside the Airways

Patients with atopic syndromes often perceive symptoms from various organs. A single drug that acts on all the syndrome's manifestations would be the ideal treatment.

Montelukast (Singulair), a cysteinyl-leukotriene receptor antagonist, is well-established in treatment of allergic rhinitis and asthma.

The effect of montelukast was assessed in a randomised, double-blind, placebo-controlled crossover study of 45 pollen-sensitised subjects who had allergic symptoms from both the upper and lower airways and allergic symptoms outside the airways (conjunctivitis, oral symptoms, eczema and/or urticaria).

Montelukast was not effective in treating allergic symptoms outside the airways. It should be considered only as a drug for asthma and rhinitis.

Montelukast should not be prescribed in urticaria, conjunctivitis and atopic dermatitis.

Leukotriene Receptor Antagonists (LTRA)

Antagonists of the CysLT1 receptor (LTRA) are efficacious as controller therapy in asthma and montelukast is FDA-approved for treatment of seasonal allergic rhinitis.

Mast cells quickly generate different mediators from the metabolism of arachidonic acid: leukotrienes and prostglandins (LTC4, LTB4, PGD2). These substances are produced within minutes of IgE-receptor crosslinking on the surface of mast cells.


Eicosanoids are signaling molecules made by oxygenation of 20-carbon essential fatty acids. There are 4 families of eicosanoids (PP-LT): prostaglandins (PG), prostacyclins (PGI), leukotrienes (LT) and thromboxanes (TX).


Mast cell mediators including (PP-LT): prostaglandins (PG), prostacyclins (PGI), leukotrienes (LT) and thromboxanes (TX). See more Allergy and Immunology mind maps here.

What is the most potent bronchoconstrictor?

(A) LTB4
(B) LTC4
(C) acetylcholine
(D) histamine
(E) thromboxane A2 (TXA2)
(F) methacholine

Answer: B

CysLTs are the most potent bronchoconstrictor agents yet discovered, about 100-1000 times more potent than histamine. The second most potent bronchoconstrictor is thromboxane A2 (TXA2).

Cysteinyl‐LTs and LTB4 are, respectively, the most potent bronchoconstrictor agents and one of the most effective leukocyte chemotaxins yet.

References:

Montelukast Is Not Effective in Controlling Allergic Symptoms Outside the Airways. A Randomised Double-Blind Placebo-Controlled Crossover Study. Lehtimäki L, Petäys T, Haahtela T. Int Arch Allergy Immunol. 2009 Jan 6;149(2):150-153.
Urinary leukotriene E(4)/exhaled nitric oxide ratio predicts montelukast response in childhood asthma http://goo.gl/i5cG
Montelukast failure index that may be helpful in predicting response in patients with asthma http://goo.gl/AzRPF
Mast Cells and Basophils. Allergy Cases.
Pathogenesis of Asthma. Allergy Cases.
Image source: Montelukast, from Wikipedia, the free encyclopedia, public domain.

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