Effective antitussives for the cough patient: an unmet need

Chronic cough is a prevalent symptom in the community but it is likely that only a small fraction of chronic coughers seek medical attention. Chronic cough can be controlled by addressing the 'cause' of the cough, but not all cough is controlled using this approach; an 'idiopathic' cough or cough of unknown aetiology is becoming more well-recognized. In these patients and in those whose cough has not responded to treatment of the cause(s), there is a lack of efficacious antitussive therapies ('non-specific' antitussives). Even in those whose cough is controlled by treatment of the cause, an efficacious antitussive for symptomatic relief would be useful for breakthrough symptoms. It is necessary to address the mechanisms underlying chronic cough, particularly the process of sensitization, both peripherally and centrally, that is the basis of chronic cough; such a process may persist even in the absence of the initiating event that first induced the cough. Currently-available antitussives in both acute and chronic cough are not very effective. Novel targets that may result in effective antitussives have been identified and with the development of clinical tools to measure cough accurately and reliably (e.g. cough counts and cough-specific quality-of-life questionnaires) and the evoked cough response (e.g. citric acid or capsaicin challenges), clinical trials should be performed. The chronic cough population is clinically heterogeneous but is characterized by an enhanced cough reflex; this should be the target population for study. Patients with chronic cough are in desperate need of effective antitussives that can be used either on demand or on a long-term basis.