Re: why might it be dangerous for a heavy smoker to use a cough suppressant?

Heavy smokers have increased bronchial secretions due to the irritant effects of the inhaled smoke. Coughing is a normal(and exagerated in smokers) mechanism to clear the airways of excess secretions. Cough suppressants may lead to failure to clear the respiratory tree with resulting plugging of the bronchi and other air passages. Areas then distal to the plugging can become infected and non functioning in air exchange. This condition is pneumonitis and ultimately pneumonia. Hence cough suppressants are really suppressing a very protective mechanism. See Cecil & Loeb, Textbook of Medicine 21st Ed. Chap. viii, Respiratory Diseases. R.K. McGregor M.D.