Asthma is a common disorder associated with the respiratory system; it affects one in four primary school children, one in seven teenagers, and one in ten adults in Australia (Bryant et al, 2002). There are many mediators involved in the pathogenesis of an asthma attack, and the severity of the symptoms can vary between individuals. There are several drugs that have been developed to treat the disorder, with differing mechanisms of action such as sympathomimetics, corticosteroids, leukotriene receptor antagonists and mast-cell stabilizers. This case deals with the leukotriene receptor antagonist montelukast. Montelukast has been shown to be particularly effective in treating children with both mild persistent asthma and frequent episodic asthma (Knorr et al, 2001; Nat. Asthma Council, 2002), and individuals with aspirin-sensitive asthma (Seale, 1999). It is given orally as the sodium salt of this compound (Singulair Product Information, 2003), the structural formula is shown below
Pathophysiology of Asthma
As already stated, asthma is a disorder of the respiratory system, it occurs when the passage in and out becomes obstructed due to reversible bronchoconstricition, chronic inflammation of the epithelium of the airways, and increased mucous secretion (Bryant et al, 2002).
There are many factors involved in the pathogenesis of asthma; such as leukotrienes, histamine, prostaglandins and other cytokines. There are two main types of asthma; extrinsic (atopic, allergic) and intrinsic. Extrinsic asthma is triggered by substances that are not normally found in the body such as allergens like pollen, dust mites and animal fur. Intrinsic is
Mechanism of Action of Montelukast
Put simply, montelukast is a reversible, competitive antagonist of leukotrienes selective for the CysLT1 receptor. The leukotrienes are products of arachidonic acid metabolism by 5-lipoxygenase (Borgeat et al, 1976), as shown in figure 1; there are 5 leukotrienes: LTA4, LTB4, LTC4, LTD4 and LTE4, of which...