The drug atlas
Respiratory/Methylxanthinelow yield
Theophylline / aminophylline
also: methylxanthine · aminophylline
Overview
An older oral/IV bronchodilator — narrow therapeutic index and many interactions, so a later-line/specialist option.
Mechanism
Non-selective phosphodiesterase inhibitor (↑cAMP) + adenosine-receptor antagonism → bronchodilation. Narrow therapeutic window → levels required.
Indications
- Asthma / COPD (add-on, specialist)
- Acute severe asthma (IV aminophylline — senior decision)
Adverse effects
Toxicity: tachyarrhythmia, seizures, vomitingserious
Narrow index — monitor levels.
Hypokalaemia (additive with β₂-agonists)common
Cautions & contraindications
CYP inhibitors raise levels → toxicityall
Macrolides, ciprofloxacin, fluconazole; smoking cessation also raises levels.
Interactions
- CYP1A2/3A4 inhibitors (macrolides, ciprofloxacin) ↑levels; inducers (rifampicin, smoking) ↓levels
Monitoring & kinetics
Plasma theophylline levels; K⁺; ECG
Oral (theophylline) / IV (aminophylline). Check levels.
Choosing it
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Source: BNF — Theophylline