Open-label Study of the Effects of Montelukast in Patients With Chronic Cough

Coughing

Montelukast, a leukotriene receptor antagonist, is likely to be effective in the treatment of chronic cough and this could be made objective by measuring cough threshold before and after two weeks of treatment.

Chronic cough is typically defined as cough that persists for longer than 8 weeks and is the most common presenting symptom in adults who seek medical treatment in an ambulatory setting. Prospective studies have shown that three conditions account for the etiologic cause of chronic cough in the largest part of immunocompetent, nonsmoking patients with normal chest radiograph findings. In order of frequency, they are upper airway cough syndrome (UACS), previously referred to as postnasal drip syndrome (PNDS), asthma and gastroesophageal reflux disease (GERD). UACS comprises many different conditions including PNDS, acute sinusitis, allergic rhinitis, non-allergic rhinitis (postinfectious rhinitis, rhinitis medicamentosa, vasomotor rhinitis, rhinitis due to physical or chemical irritants). Cough occurs in all asthmatics, and in a subset of patients with cough-variant asthma (CVA), it is the only presenting symptom. In these cases it is well controlled with inhaled corticosteroids and beta-2 agonists. GERD is another cause that should be contemplated when anti-tussive or anti-inflammatory/anti-allergic treatment do not render results and when there are presenting symptoms suggestive of it. Moreover, factors like smoking and use of ACE-inhibitors should also be taken into account. Leukotrienes are very important agents in the inflammatory response. It is known that they are contributing significantly to the pathological processes in asthma. Montelukast is a leukotriene receptor antagonist which blocks the bonding of leukotrienes to their receptors thus inhibiting their inflammatory, bronchoconstrictive and mucosecretory effects. Multiple clinical trials have demonstrated the ability of the leukotriene antagonists to improve symptoms, pulmonary function and bronchial hyperresponsiveness in patients with asthma. However, not much is known about their effects in people with chronic cough. Studies have been carried out in an attempt to find out the effects of montelukast in some forms of chronic cough. Nevertheless, the impact of montelukast on objective parameters such as cough reflex threshold, has not been explored. The investigators also reckon that montelukast will affect exhaled breath temperature - a novel surrogate marker of airway inflammation recognized lately

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