Theophylline is one of those medications that has intrigued and possibly confused clinicians and pharmacologists alike since the mid 19th century. Related agents caffeine and theobromine were used in the 1930s as bronchodilators, and theophylline developed an established place in the management of acute airflow obstruction associated with asthma and chronic obstructive pulmonary disease (COPD) during the mid 1900s.¹

Pharmacologically, theophylline is characterised principally as a phosphodiesterase (PDE) inhibitor. Its main biological action is to block the inactivation of cyclic AMP and cyclic GMP giving rise to bronchodilation, increased ciliary beat frequency, and reduced inflammatory cell numbers in the airways. However, it has been observed that other PDE inhibitors do not exert such effects, which suggests that other activities may be relevant. Theophylline also acts as an adenosine receptor antagonist, which may be relevant to its desirable effects and probably gives rise to a number of the side effects seen with use of this agent …