Pharmacological and non-pharmacological interventions for cough in adults with respiratory and non-respiratory diseases: A systematic review of the literature

The management of cough in adults with respiratory and non-respiratory illnesses is suboptimal and based mostly on clinical opinions rather than evidence. A systematic review was carried out assessing all trials in adult patients with respiratory and non-respiratory diseases (excluding cancer) that had chronic cough as primary or secondary outcome. A total of 1177 trials were retrieved and 75 met the criteria for inclusion in the review. The vast majority were in patients with asthma and chronic obstructive pulmonary disease (COPD). Cough was the primary outcome in less than one-quarter of the studies. The measurement of cough was variable, mostly using unvalidated scales or being part of an overall 'symptoms' score. Positive results were overall seen with the use of corticosteroids, leukotriene receptor antagonists, mast cell stabilizers, ipratropium bromide, neltenexine, iodinised glycerol and lidocaine. Speech pathology training and symptom monitoring through SMS messages (accompanied by treatment adjustments) have also shown promise. Evidence for established anti-tussive agents such as codeine was scarce, with positive studies from the 1960s, whilst more recent studies showed no effect in patients with COPD. Many studies had conflicting results. It is imperative that the management of cough and its evidence base be improved, using higher quality research designs and with cough being the primary outcome of trials.