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Theophylline (Theo-24, Theochron)

Methylxanthine bronchodilator (high-alert; narrow therapeutic index)

Mechanism of action

Inhibits phosphodiesterase, raising cAMP in bronchial smooth muscle, producing bronchodilation. Also stimulates the central respiratory drive and has mild diuretic and inotropic effects. Largely supplanted by inhaled bronchodilators and corticosteroids; still used in select asthma and COPD patients and in apnea of prematurity.

Adverse effects

Life-threatening / NCLEX-tested

  • Theophylline toxicity — therapeutic 10–20 mcg/mL; > 20 toxic; > 30 severe
  • Tachyarrhythmias, including SVT and ventricular tachycardia
  • Seizures (sometimes the first sign of severe toxicity)
  • Severe hypotension
  • Hyperglycemia and hypokalemia (severe toxicity)
  • GI hemorrhage from severe nausea/vomiting

Side effects

Common — what to teach

  • Nausea, vomiting (often the first sign of an elevated level)
  • Insomnia, restlessness, anxiety
  • Tremor
  • Headache
  • Diuresis
  • Palpitations

Food & drug interactions

Many — theophylline is metabolized via CYP1A2 and CYP3A4. RAISES levels: cimetidine, ciprofloxacin and other fluoroquinolones, erythromycin, clarithromycin, fluconazole, oral contraceptives, allopurinol, propranolol. LOWERS levels: rifampin, phenytoin, carbamazepine, smoking (nicotine induces metabolism — quitting smoking raises levels). Caffeine compounds CNS and cardiac effects.

Nursing implications

Assessment, monitoring, patient teaching

  • Check theophylline level periodically; recheck after dose changes, drug additions, smoking cessation, or new illness
  • Teach patients to take at the same times each day, with food to limit GI upset
  • Counsel against caffeine (coffee, tea, energy drinks) — additive CNS and cardiac stimulation
  • Teach early toxicity signs: nausea, vomiting, restlessness, palpitations, tremor — STOP and call
  • Smoking cessation is a level-raiser — alert the prescriber when patients quit
  • Two-nurse verification for IV doses — high-alert medication

When to hold / contraindications

  • Theophylline level > 20 mcg/mL with symptoms (or any level with toxicity)
  • Active tachyarrhythmia or new ventricular ectopy
  • Active seizure or neuro changes that could be toxicity
  • Severe vomiting (oral) — discuss IV transition or hold
  • Initiation of an interacting drug (e.g., ciprofloxacin) without dose adjustment

Memory anchor

Theophylline 10–20 mcg/mL therapeutic; vomiting + tremor + tachy = toxic. Nicotine speeds metabolism; quitting smoking raises levels. Avoid caffeine.

Reminder: Drug cards are study aids, not clinical guidance. Always cross-check doses, holds, and contraindications with your facility's formulary and your clinical instructors before patient care.

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