Theophylline is a drug, a phosphodiesterase (PDE) inhibitor, that is widely used in therapy for respiratory diseases. It bears structural and pharmacological similarity to caffeine. It is naturally found in black tea and green tea.

The main actions of theophylline are:

• relaxation of bronchial smooth muscle
• positive inotropic (increases heart muscle contractility and efficiency)
• positive chronotropic (increases heart rate)
• lowers blood pressure
• increases renal blood flow
• some anti-inflammatory effect

The use of theophylline is complicated by the fact that it interacts with various drugs, chiefly cimetidine and phenytoin

The main therapeutic uses of theophylline are:

• chronic obstructive diseases of the airways
  • chronic obstructive pulmonary disease COPD
  • bronchial asthma