Persistent cough: causes and cures.

Refractory cough in a patient with a normal chest X-ray usually falls into one of five categories: drug-induced (especially by ACE inhibitors), secondary to postnasal discharge, gastroesophageal reflux, or hyperactive airway disease, and idiopathic but responsive to nebulized lidocaine. The history may point to the most likely cause, and empiric therapy may confirm the diagnosis.