The patient with chronic cough.

The most effective management of cough is specific therapy, which results in a greater than 90% response rate, so the cause should be thoroughly investigated. A chest x-ray should be taken early in the clinical investigation of chronic cough. The three most common causes of chronic cough when chest x-rays are normal are postnasal drip, bronchial asthma and gastro-oesophageal reflux. Chronic cough has more than one cause in 20% of patients, so therapy may need to be directed at multiple causes. Gastro-oesophageal reflux may complicate cough from any cause because a cough-reflux feedback cycle can develop. Hence, a four-week trial of an H2-receptor antagonist is indicated in patients with unexplained chronic cough where the history, physical examination, chest x-ray, lung function tests, ear/nose/throat examination and home peak flow monitoring all fail to elucidate a cause. Non-specific therapy should be reserved for when no diagnosis can be made, or when therapy is likely to be ineffective (e.g., lung malignancy).