Used for treating active symptoms and blockage of airway due to asthma or other lung diseases such as emphysema or bronchitis. It is used in combination with other medicines. Aminophylline is a xanthine derivative. It works by relaxing the smooth muscle surrounding the bronchial tubes (air passages) of the lungs, allowing the tubes to widen, making breathing easier. Aminophylline improves contraction of the diaphragm (the major breathing muscle).