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Theophylline is a methylxanthine drug used in therapy for respiratory diseases under a variety of brand names. As a member of the xanthine family, it bears structural and pharmacological similarity to caffeine. It is naturally found in black tea and green tea. more...

The main actions of theophylline are:

• relaxing of bronchial smooth muscle
• positive inotropic (increasing heart muscle contractility and efficiency)
• positive chronotropic (increasing heart rate)
• lowering of blood pressure
• increase of renal blood flow
• some anti-inflammatory effects.

The use of theophylline is complicated by the fact that it interacts with various drugs, chiefly cimetidine and phenytoin, and that it has a narrow therapeutic index, so its use must be monitored to avoid toxicity. It can also cause nausea, diarrhœa, increase in heart rate, arrhythmias and CNS excitation. Its toxicity is increased by erythromycin, cimetidine and fluoroquinolones.

The main therapeutic uses of theophylline are:

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

A proposed mechanism of action includes a non-specific inhibition of phosphodiesterase enzymes, producing an increase in intracellular cyclic AMP; however, this is not known with certainty.

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