Montelukast - How It Works
Clinical pharmacology details from the US FDA-approved label: how Montelukast works in your body, how it's absorbed, how long it stays active, and how it's eliminated.
Mechanism of Action
12.1 Mechanism of Action The cysteinyl leukotrienes (LTC 4 , LTD 4 , LTE 4 ) are products of arachidonic acid metabolism and are released from various cells, including mast cells and eosinophils. These eicosanoids bind to cysteinyl leukotriene (CysLT) receptors. The CysLT type-1 (CysLT 1 ) receptor is found in the human airway (including airway smooth muscle cells and airway macrophages) and on other pro-inflammatory cells (including eosinophils and certain myeloid stem cells). CysLTs have been correlated with the pathophysiology of asthma and allergic rhinitis. In asthma, leukotriene-mediated effects include airway edema, smooth muscle contraction, and altered cellular activity associated with the inflammatory process. In allergic rhinitis, CysLTs are released from the nasal mucosa after allergen exposure during both early-and late-phase reactions and are associated with symptoms of allergic rhinitis. Montelukast is an orally active compound that binds with high affinity and selectivi
12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action The cysteinyl leukotrienes (LTC 4 , LTD 4 , LTE 4 ) are products of arachidonic acid metabolism and are released from various cells, including mast cells and eosinophils.
These eicosanoids bind to cysteinyl leukotriene (CysLT) receptors.
The CysLT type-1 (CysLT 1 ) receptor is found in the human airway (including airway smooth muscle cells and airway macrophages) and on other pro-inflammatory cells (including eosinophils and certain myeloid stem cells).
CysLTs have been correlated with the pathophysiology of asthma and allergic rhinitis.
In asthma, leukotriene-mediated effects include airway edema, smooth muscle contraction, and altered cellular activity associated with the inflammatory process.
In allergic rhinitis, CysLTs are released from the nasal mucosa after allergen exposure during both early-and late-phase reactions and are associated with symptoms of allergic rhinitis.
Montelukast is an orally active compound that binds with high affinity and selectivity to the CysLT 1 receptor (in preference to other pharmacologically important airway receptors, such as the prostanoid, cholinergic, or β-adrenergic receptor).
Montelukast inhibits physiologic actions of LTD 4 at the CysLT 1 receptor without any agonist activity.
12.2 Pharmacodynamics Montelukast causes inhibition of airway cysteinyl leukotriene receptors as demonstrated by the ability to inhibit bronchoconstriction due to inhaled LTD 4 in asthmatics.
Doses as low as 5 mg cause substantial blockage of LTD 4 -induced bronchoconstriction.
In a placebo-controlled, crossover study (n=12), montelukast sodium inhibited early- and late-phase bronchoconstriction due to antigen challenge by 75% and 57%, respectively.
The effect of montelukast sodium on eosinophils in the peripheral blood was examined in clinical trials.
In patients with asthma aged 2 years and older who received montelukast sodium, a decrease in mean peripheral blood eosinophil counts ranging from 9% to 15% was noted, compared with placebo, over the double-blind treatment periods.
In patients with seasonal allergic rhinitis aged 15 years and older who received montelukast sodium, a mean increase of 0.2% in peripheral blood eosinophil counts was noted, compared with a mean increase of 12.5% in placebo-treated patients, over the double-blind treatment periods; this reflects a mean difference of 12.3% in favor of montelukast sodium.
The relationship between these observations and the clinical benefits of montelukast noted in the clinical trials is not known [ see Clinical Studies ].
12.3 Pharmacokinetics Absorption Montelukast is rapidly absorbed following oral administration.
After administration of the 10-mg film-coated tablet to fasted adults, the mean peak montelukast plasma concentration (C max ) is achieved in 3 to 4 hours (T max ).
The mean oral bioavailability is 64%.
The oral bioavailability and C max are not influenced by a standard meal in the morning.
For the 5-mg chewable tablet, the mean C max is achieved in 2 to 2.5 hours after administration to adults in the fasted state.
Pharmacokinetics
12.3 Pharmacokinetics Absorption Montelukast is rapidly absorbed following oral administration. After administration of the 10-mg film-coated tablet to fasted adults, the mean peak montelukast plasma concentration (C max ) is achieved in 3 to 4 hours (T max ). The mean oral bioavailability is 64%. The oral bioavailability and C max are not influenced by a standard meal in the morning. For the 5-mg chewable tablet, the mean C max is achieved in 2 to 2.5 hours after administration to adults in the fasted state. The mean oral bioavailability is 73% in the fasted state versus 63% when administered with a standard meal in the morning. For the 4-mg chewable tablet, the mean C max is achieved 2 hours after administration in pediatric patients 2 to 5 years of age in the fasted state. The 4-mg oral granule formulation is bioequivalent to the 4-mg chewable tablet when administered to adults in the fasted state. The safety and efficacy of montelukast sodium in patients with asthma were demonstrated in clinical trials in which the 10-mg film-coated tablet and 5-mg chewable tablet formulations were administered in the evening without regard to the time of food ingestion. The safety of montelukast sodium in patients with asthma was also demonstrated in clinical trials in which the 4-mg chewable tablet formulation was administered in the evening without regard to the time of food ingestion. The safety and efficacy of montelukast sodium in patients with seasonal allergic rhinitis were demo