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Methylxanthine Bronchodilator Pregnancy: Compatible with monitoring — neonatal tachycardia and irritability reported if taken near delivery

Theophylline (Oral Modified Release)

Brand names: Uniphyllin, Slo-Phyllin, Nuelin SA

Adult dose

Dose: 175–500 mg BD (modified release). Usual maintenance: 200–300 mg BD
Route: Oral (modified release — swallow whole, do not crush)
Frequency: Twice daily
Max: 900 mg/day in divided doses
Narrow therapeutic index. Target plasma level: 10–20 mg/L (55–110 micromol/L). Different brands are NOT interchangeable. Always prescribe by brand.

Paediatric dose

Route: Oral (divided BD doses)
Frequency: BD
Max: 800 mg/day
BNF for Children: NARROW THERAPEUTIC INDEX — do NOT calculate without TDM. Loading: 5 mg/kg oral/IV (omit if already on theophylline/aminophylline). Maintenance: 12–24 mg/kg/day in 2 divided doses (modified release). Target plasma level 10–20 mg/L. Weight-based calculator disabled — requires TDM-guided dosing. Source: BNF for Children 2024

Dose adjustments

Renal

No dose adjustment required; haemodialysis removes some drug

Hepatic

Reduce dose significantly in hepatic impairment — greatly reduced clearance

Clinical pearls

  • Narrow therapeutic window — toxicity occurs near therapeutic levels; monitor levels
  • Plasma level 5 mg/L after 4–6h following 8h MR dose
  • Smoking cessation: theophylline levels may rise significantly when patient quits smoking (CYP1A2 induction reversal)
  • Do NOT swap brands — different release profiles lead to unpredictable levels

Contraindications

  • Acute porphyria
  • Current use of IV aminophylline (same drug)

Side effects

  • Nausea/vomiting (early toxicity)
  • Headache
  • Palpitations
  • Tachyarrhythmias (toxicity)
  • Seizures (severe toxicity)
  • Insomnia
  • Tremor

Interactions

  • Erythromycin/clarithromycin — inhibit clearance (increase levels by 25–40%)
  • Ciprofloxacin — doubles theophylline levels
  • Rifampicin — induces clearance (reduces levels)
  • Smoking — induces CYP1A2 (reduces levels by 50%)
  • Cimetidine — increases levels
  • Phenytoin — reduced phenytoin and theophylline levels

Monitoring

  • Plasma theophylline levels (target 10–20 mg/L)
  • Heart rate and ECG
  • Enquire about smoking status
  • Level measurement: trough (before morning dose) for MR preparations

Reference: BNFc; BNF; BTS/SIGN Asthma Guidelines 2019; GOLD COPD 2024. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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