Cough is the most frequently encountered symptom affecting humans, with prevalence rates estimated within the range 5–40%. Acute or short lived cough, occurring commonly in relationship with viral upper respiratory infection usually resolves on its own in duration of few days.

On contrary, persistent cough can be related to substantial morbidity including sleep loss, exhaustion, irritability, urinary stress incontinence, cough syncope, impaired performance in daily activities, and significant social disability. The present study highlights several important features in the management of persistent dry cough.

The history alone is unreliable diagnostic tool as most patients may have clinically silent potential underlying cause of cough. Patients may have characteristic features in the history indicative of a particular diagnosis but even then become unresponsive to specific treatment for that condition.

However, investigation may propose an alternative diagnosis and the positive predictive value of the history alone for a specific underlying condition was found to be alone 40–56%.

Moreover, the study also substantiated the previous observation that patients with dry cough show increased capsaicin sensitivity which normalises with successful treatment of the cough. This can be verified for all treatment groups and concludes that heightened sensitivity of afferent cough nerves is a crucial pathogenetic mechanism in patients with persistent dry cough, irrespective of the specific aetiology.

Therefore, it can be concluded that specific treatment of the underlying cause is impossible for patients with idiopathic persistent dry cough and treatment must be dependent on antitussive therapy.

Cough sensitivity to inhaled tussigens such as capsaicin is also improved in these patients, indicative of the fact that an ideal antitussive drug can decrease this altered sensitivity to normal, without substantial adverse effects. Recent researchers demonstrated that calcitonin gene-related peptide and substance P may contribute in the pathogenesis of idiopathic persistent dry cough, and antagonists of these compounds may act as a potential antitussive treatment, which further require more studies.

Source: O’Connell F. Management of persistent dry cough. Thorax 1998;53:723-724.