Xanthines in Respiratory Therapy

  • Xanthines Overview

    • Definition: Xanthines are methylxanthine compounds used in respiratory therapy.

  • Clinical Uses

    • Theophylline: Treats asthma, COPD, and apnea of prematurity.
    • Asthma: Sustained-release theophylline for maintenance therapy (step 2, >5 years). Alternative in step 3 with ICS.
    • COPD: Theophylline alternative to other bronchodilators (not for acute exacerbations).
    • Apnea of Prematurity: Methylxanthines first-line; caffeine citrate preferred due to safety and efficacy.

  • Xanthine Agents

    • Theophylline (tea leaves), Theobromine (cocoa), Caffeine (coffee, cocoa).

  • Pharmacological Properties

    • CNS stimulation, cardiac muscle stimulation, diuresis, bronchodilation, vasodilation, and headache relief.

  • Mechanism of Action

    • Unknown; potential smooth muscle relaxation via phosphodiesterase inhibition and adenosine antagonism.

  • Dosing Considerations

    • Titration necessary due to individual metabolism.
    • Recommended serum levels: 5-15 μg/mL for asthma, 5-10 μg/mL for COPD.

  • Toxicity and Side Effects

    • Narrow therapeutic margin: side effects may include nausea, cardiac arrhythmias, headache, anxiety, and gastric upset.

  • Factors Affecting Theophylline Activity

    • Increases: liver disease, viral hepatitis. Decreases: smoking.

  • Recent Guidelines

    • Xanthines not first-line for asthma/COPD; considered after other treatments fail.

  • Nonbronchodilating Effects

    • Enhances respiratory muscle contractility and endurance; cardiovascular benefits.

  • Respiratory Care Assessment

    • Before: assess effectiveness, monitor flow rates, respiratory assessment, and blood levels.
    • During: subjective reactions, blood gases or pulse oximetry.
    • Long Term: pulmonary function studies, educate on peak flow meters, and emphasize limitations of xanthines in treating inflammation.