Theophylline is used as a bronchodilator for treatment of moderate to severe asthma and chronic obstructive pulmonary disease (COPD).

TDM is needed for theophylline because the kinetics of the drug are highly variable. It has a narrow therapeutic window, and overdose can result in elevated heart rate, arrhythmia, and CNS excitability.

Clearance of the drug is increased in children, smokers, persons with cystic fibrosis, and persons with hyperthyroidism. Elimination is slowed in congestive heart failure and in the elderly.