Aminophylline is a compound of the bronchodilator theophylline with ethylenediamine in 2:1 ratio. The ethylenediamine improves solubility, and the aminophylline is usually found as a dihydrate. Aminophylline is less potent and shorter-acting than theophylline. Its most common use is in the treatment of airway obstruction from asthma or COPD. It is used off-label as a reversal agent during nuclear stress testing. Aminophylline is a nonselective adenosine receptor antagonist and phosphodiesterase inhibitor.