Doxofylline (7-(1, 3-dioxalan-2-ylmethyl) theophylline) is a novel xanthine bronchodilator which differs from theophylline in that it contains a dioxalane group in position 7. Doxofylline is indicated for the treatment of bronchial asthma, pulmonary disease with spastic bronchial component and Chronic Obstructive Pulmonary Disease (COPD). Doxofylline does not directly inhibit any of the known HDAC enzymes, and did not inhibit any phosphodiesterase (PDE) enzyme sub types or act as an antagonist at any of the known adenosine receptors, except for PDE2A(1), and adenosine A(2A) and only at the highest tested concentration (10(-4) M). Doxofylline has greatly decreased affinity towards adenosine A1 and A2 receptors, which explain its better safety profile. Moreover, it does not interfere with calcium influx into the cells nor antagonize calcium channel blockers. Doxofylline has been shown to be a more potent bronchodilator with fewer side effects than theophylline. This drug should not be administered together with other xanthine derivatives, including beverages and foods containing caffeine.

Etamiphylline is the respiratory stimulant. No information is available about pharmacodynamics of etamiphylline. No human pharmacokinetic data are available. Etamiphylline seems to be a rather weaker bronchodilator than theophylline when administered orally.