Theophylline, consider Adenosine

Theophylline is also considered an alternative to inhaled corticosteroids for the treatment of mild persistent asthma however, limited efficacy compared to inhaled corticosteroids, a narrow therapeutic index with life-threatening toxicity, and multiple clinically important drug interactions have severely limited its use. Theophylline causes bronchodilation through inhibition of phosphodiesterase and antagonism of adenosine and appears to have anti-inflammatory and immunomodulatory properties as well.36... 

Natural antagonists for ARs, such as caffeine and theophylline show in general low affinity for the A3 AR subtype (Baraldi et al. 2003). In a recent work, the approach based on the annelation of xanthine derivatives for the development of adenosine receptors antagonists has been extensively considered (Drabczy ska et al. 2003). 

Theophylline, available under many proprietary names, relaxes bronchial smooth muscles to relieve or prevent asthma. The therapeutic effect of theophyUine is likely due to antagonism of adenosine receptors in smooth muscle, whereas the toxic effects are due to inhibition of cyclic nucleotide phosphodiesterase. With increased use of p-adrenergic agonists, and because of the considerable toxicity associated with it, theophylline is now considered... 

Theophylline is a competitive antagonist at adenosine receptors. Adenosine can act as an autacoid and transmitter with myriad biological actions. Of particular relevance to asthma are the observations that adenosine can cause bron-choconstriction in asthmatics and potentiate immunologi-cally induced mediator release from human-lung mast cells. Inhibition of the actions of adenosine therefore also must be considered when attempting to explain the mechanism of action of theophylline. 

It is usually considered that an adenosine bolus for the termination of paroxysmal supraventricular tachycardia will be ineffective in patients taking xanthines. However, one case describes a man taking theophylline (serum level 8 nanograms/mL) in whom adenosine 9 mg terminated supraventricular tachycardia. Two previous adenosine doses, one of 3 mg and one of 6 mg had not been effective. Another report found that high adenosine doses, of 400 to 800 micrograms/kg (usual dose 50 to 200 micrograms/kg), were required to revert supraventricular tachycardia in a preterm infant receiving theophylline. ... 

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