Theophylline

Summary

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Key Points

• Methylxanthine (Theophylline, aminophylline)
  • Mechanism
    •  Bronchodilation
      • Phosphodiesterase inhibitor
        • ↑ cAMP causes relaxation of smooth muscles in the airways.
        • Theophylline, a phosphodiesterase inhibitor, results in increased intracellular cyclic AMP, which contributes to its role as a bronchodilator. Theophylline also has anti-inflammatory effects, although they are far less potent than glucocorticoids.
      • Adenosine receptor antagonist
        • Adenosine normally causes bronchoconstriction.
        • Theophylline is an adenosine receptor antagonist and indirect adrenergic agent with a narrow therapeutic index.
  • Indications
    • COPD
    • Asthma (rarely used)
      • Leukotriene antagonists and theophylline have not been shown to be effective in patients with severe uncontrolled asthma
  • Adverse Effects
    • Metabolized by cytochrome P450
      • It is predominantly metabolized by the hepatic cytochrome oxidases. Inhibition of these enzymes by concurrent illness (eg, infection with fever) or drugs (ag, cimetidine, ciprofloxacin, macrolides, verapamil) can raise serum concentration and cause toxicity (eg, seizures, cardiac arrhythmias).
    • Narrow therapeutic index with risk for toxicity
      • Tachyarrhythmias
      • Seizures
      • Abdominal pain
      • Nausea
      • Other symptoms and signs: tremor, headache, anxiety, hypokalemia, hyperglycemia.