The cough is one of the most common symptoms for which patients have to take physicians and pulmonologists consultation, because it sometime can so intensely and adversely affect the quality of patients' lives. The cough is an important characteristic of the larynx and respiratory system which help
out in the removal of foreign substances and secretions and prevent aspiration of food and fluids and thus prevent choking (suffocation) which may provoked by the presence of such agents. Additionally, some of the drugs like ACE inhibitors also induce cough due to over production of bradykinin, which intern cause
hyperactivity of cough reflex or fentanyl can provoke coughing by inducing a pulmonary chemo-reflex in 50% of patients; this is inhibited by terbutaline.