<p>Theophylline is a naturally occurring methylxanthine, belonging to the same family as caffeine. Although it has seen a decline in popularity over recent years, it is still prescribed for the treatment of asthma and chronic obstructive pulmonary disease. As well as its bronchodilatory effects, theophylline also has anti-inflammatory and immunomodulatory actions and increases respiratory drive. These findings may well reverse the downward trend in prescribing.</p>