Theophylline — NZ Medication Guide
📋 Reviewed by a Registered Pharmacist NZ — This information is for general educational purposes only and does not replace professional medical advice. Always consult your doctor or pharmacist before starting, stopping, or changing any medication.
What is Theophylline?
Theophylline is a xanthine bronchodilator used for COPD and severe persistent asthma in patients who have not responded to other treatments. This medication is funded by Pharmac for severe asthma and COPD as an add-on therapy.
What is Theophylline Used For?
Theophylline is used as a third-line bronchodilator for COPD and severe persistent asthma that is not adequately controlled with inhaled therapies. It has a narrow therapeutic index and is less commonly used now than previously.
How Does Theophylline Work?
Theophylline inhibits phosphodiesterase enzymes (PDEs), increasing intracellular cyclic AMP in bronchial smooth muscle — causing relaxation and bronchodilation. It also has anti-inflammatory properties at lower concentrations and may improve diaphragmatic contractility in COPD.
How to Take Theophylline
Taken as modified-release tablets twice daily (Nuelin SA®, Bronchodil®). Dose is adjusted to achieve a therapeutic serum level of 10–20 mg/L (older target — some guidelines now use lower levels). Serum theophylline levels must be monitored, particularly when starting, changing dose, or starting interacting medicines.
Common Side Effects of Theophylline
- Nausea and vomiting (common)
- Headache
- Palpitations and tachycardia
- Tremor
- Insomnia
- Increased diuresis
Serious Side Effects — Seek Medical Attention
Contact your doctor or call 111 immediately if you experience any of the following:
- Theophylline toxicity — seizures, cardiac arrhythmias (at serum levels >20 mg/L)
- Severe nausea and vomiting (early toxicity warning)
- Atrial fibrillation and ventricular tachycardia
Drug Interactions
Theophylline may interact with other medicines. Always inform your doctor and pharmacist of all medications you are taking. Key interactions include:
- MANY interactions due to CYP1A2 metabolism
- Ciprofloxacin and erythromycin (increase theophylline levels — toxicity risk)
- Carbamazepine, phenytoin, rifampicin (reduce theophylline levels)
- Smoking (increases clearance — stopping smoking increases levels)
- Fluvoxamine (markedly increases levels)
- Caffeine (additive effects)
New Zealand Prescribing Information
Theophylline modified-release tablets (Nuelin SA® 175 mg, 350 mg; Bronchodil® 300 mg) are funded by Pharmac as a third-line agent. Due to its narrow therapeutic index, many significant drug interactions, and the availability of safer alternatives, theophylline use has declined substantially. Serum level monitoring is mandatory. Any illness, change in smoking status, or addition of an interacting medicine requires a level check.
Frequently Asked Questions
How will I know if theophylline levels are too high?
Early signs of toxicity include persistent nausea, vomiting, insomnia, headache, and tremor. Severe toxicity causes seizures and dangerous heart arrhythmias. Regular blood level monitoring and prompt reporting of any new symptoms is essential.
Why did my theophylline dose need adjustment when I quit smoking?
Smoking increases the rate at which the liver metabolises theophylline. When you stop smoking, theophylline clearance decreases and blood levels can rise significantly — potentially to toxic levels. Your doctor must recheck your theophylline level and adjust the dose when you quit.
⚠️ Disclaimer: This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified health provider. In New Zealand, medication availability and funding may vary — check with Pharmac or your pharmacist for current information.
Reviewed by a Registered Pharmacist NZ
References & Further Information
The following New Zealand and international resources were used to inform this page: