Overview
Theophylline is a methylxanthine bronchodilator used for the treatment of reversible airflow obstruction in chronic asthma, chronic bronchitis, and emphysema. It requires careful dose titration and therapeutic drug monitoring due to its narrow therapeutic index and significant interpatient variability in metabolism.
Mechanism of Action
Theophylline acts as a nonselective phosphodiesterase inhibitor, increasing intracellular cyclic AMP levels, and as an adenosine receptor antagonist, leading to bronchodilation, anti-inflammatory effects, and improved diaphragmatic contractility.
Indications
- Treatment of symptoms and reversible airflow obstruction associated with chronic asthma
- Management of chronic obstructive pulmonary diseases including emphysema and chronic bronchitis
Common Doses
- 100 mg
- 200 mg
- 300 mg
- 400 mg
- 600 mg (maximum daily dose in select patients)
Dosage
Dosing is highly individualized based on patient factors and serum concentration monitoring (target 10-20 mcg/mL). Typical adult starting dose is 300-400 mg/day in divided doses, titrated upward based on tolerance and serum levels, with maximum doses not exceeding 400-600 mg/day depending on risk factors.
Contraindications
- History of hypersensitivity to theophylline or any product component
Side Effects
- Nausea, vomiting, headache, insomnia (common at therapeutic levels)
- Cardiac arrhythmias, seizures, hypotension (serious at levels >30 mcg/mL)
- Hypokalemia, hyperglycemia, metabolic disturbances
- Gastrointestinal bleeding, rhabdomyolysis
Interactions
- Cimetidine, fluoroquinolones, macrolides, and allopurinol decrease theophylline clearance
- Phenytoin, phenobarbital, rifampin, and smoking increase theophylline clearance
- Synergistic CNS/cardiac effects with sympathomimetics
Counseling Points
- Take exactly as prescribed; do not crush or chew extended-release formulations
- Report signs of toxicity: nausea, vomiting, rapid heartbeat, seizures
- Avoid excessive caffeine intake
- Inform all healthcare providers of theophylline use
- Keep regular appointments for blood level monitoring