Identification of asthmatic patients who respond to Singulair (montelukast) is important as response is variable

Leukotrienes (LTs) include cysteinyl LTs (CysLTs) and LTB(4). They are potent lipid mediators that have a role in the pathophysiology of asthma.

Receptors

2 receptor subtypes for CysLTs have been identified: CysLT(1) and CysLT(2). The activation of the CysLT(1) receptor is responsible for most of the pathophysiological effects of CysLTs in asthma, including:

- increased airway smooth muscle activity
- microvascular permeability
- airway mucus secretion

LTB(4) might have a role in severe asthma, asthma exacerbations, and the development of airway hyperresponsiveness.


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).

Medications

CysLT(1) receptor antagonists can be given orally as monotherapy in patients with mild persistent asthma, but these drugs are generally less effective than inhaled glucocorticoids (ICS).

Combination of CysLT(1) receptor antagonists (LTRA) and inhaled glucocorticoids (ICS) in patients with more severe asthma may improve asthma control and enable the dose of inhaled glucocorticoids to be reduced while maintaining similar efficacy.

The identification of subgroups of asthmatic patients who respond to CysLT(1) receptor antagonists is relevant for asthma management as the response to these drugs is variable.

CysLT(1) receptor antagonists have a potential anti-remodelling effect that might be important for preventing or reversing airway structural changes in patients with asthma.

The LTRA Singulair will be available as a significantly less expensive generic medication in August 2012.

References:

Leukotriene modifiers for asthma treatment. Montuschi P, Peters-Golden ML. Clin Exp Allergy. 2010 Dec;40(12):1732-41. doi: 10.1111/j.1365-2222.2010.03630.x.

Montelukast failure index that may be helpful in predicting response in patients with asthma http://goo.gl/AzRPF

Image source: Montelukast, from Wikipedia, the free encyclopedia, public domain.

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