A xanthine bronchodilator (breathing medicine)
Theophylline
A tablet that helps open the airways in asthma and COPD — effective but with a narrow safe range, so blood levels are monitored and the brand is kept consistent.
What is Theophylline?
Theophylline is an oral bronchodilator used as an add-on treatment in asthma and COPD to help keep the airways open. It has a narrow safe range, so blood levels are monitored, the brand is kept consistent, and it interacts with many medicines (and with smoking, which lowers its level). Signs of too much include nausea, a fast or irregular heartbeat, restlessness and, at high levels, seizures.
Education and reference only. This is a plain-language guide to Theophylline — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Theophylline is a long-established tablet used to help open the airways in asthma and chronic obstructive pulmonary disease (COPD), usually as an add-on when inhalers alone are not enough. It is effective but has fallen from first-line use because it has a narrow margin between a helpful and a toxic level, interacts with many things, and needs monitoring. A related medicine, aminophylline, is a form of theophylline used by injection in hospital. It is taken as a modified-release tablet, kept to a consistent brand.
How it works
Theophylline relaxes the muscle in the walls of the airways, widening them so air can move more freely, and it has some anti-inflammatory and breathing-stimulant effects as well. It works partly by blocking chemical signals (adenosine and phosphodiesterase enzymes) inside airway and inflammatory cells. Because it is broken down by the liver at a rate that varies a lot between people — and is changed by smoking, illness and many medicines — the blood level can swing, which is why it is measured and kept in a target range.
What it treats
Conditions Theophylline is used for
Practical use
How to take Theophylline
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it regularly as prescribed, as the same brand each time — different modified-release brands are not interchangeable.
- Swallow modified-release tablets whole (or as directed); take it consistently in relation to food as advised, since this affects absorption.
- Tell your doctor if you start or stop smoking, or start or stop any medicine — these change your theophylline level.
- Report nausea and vomiting, a fast or pounding or irregular heartbeat, tremor, restlessness or headache — these can signal the level is too high.
- If you miss a dose, take the next one as usual; do not double up.
Weighing it up
Advantages & disadvantages of Theophylline
Advantages
- An effective oral add-on when inhaled treatments are not enough.
- Provides around-the-clock bronchodilation from a modified-release tablet.
- Blood levels can be measured to guide safe dosing.
Disadvantages
- Narrow safe range with a real risk of toxicity, needing blood-level monitoring.
- Level is altered by smoking, illness and many medicines — interactions matter.
- Brands are not interchangeable, and it can lower blood potassium.
Practical use
Good to know
Theophylline's narrow safe range is the key issue: too little does not work, and too much causes nausea, a racing or irregular heartbeat, restlessness and, at high levels, fits — so the blood level is checked and kept in range. Its level is strongly affected by other factors: smoking (and stopping smoking) changes how fast it is cleared, as do many medicines and some illnesses, so tell your doctor if you start or stop smoking or start a new medicine. People are usually kept on the same brand, because different modified-release versions release the drug differently. A low blood potassium can occur, particularly if it is combined with certain other breathing medicines.
Who should not take it / use with caution
- People with certain heart-rhythm disorders or uncontrolled fast heart rhythms, used only with caution.
- Used at lower amounts and with closer monitoring in liver disease, heart failure, and in older people, where it is cleared more slowly.
- People with epilepsy or a low potassium level need particular care.
Monitoring
- Theophylline blood level (kept within a target range, checked after changes)
- Blood potassium, especially with other breathing medicines
- Heart rate and symptoms of toxicity
Side effects
- Common, especially as the level rises: nausea, stomach upset, headache, restlessness, difficulty sleeping and a fast heartbeat.
- Signs of too much: vomiting, a rapid or irregular heartbeat, marked tremor or agitation — report these; at high levels, seizures can occur.
- A low blood potassium level, particularly when combined with certain other asthma/COPD medicines.
Key interactions
- Many medicines change theophylline levels: some antibiotics (such as ciprofloxacin, clarithromycin and erythromycin) and antifungals raise it and the risk of toxicity, while others (such as rifampicin and some antiepileptics) lower it.
- Combining it with high-dose salbutamol-type inhalers or steroids or water tablets can lower potassium further.
- Smoking speeds up its breakdown (lowering levels), so starting or stopping smoking changes the amount needed.
Available as: Modified-release tablets and capsules (brand kept consistent); aminophylline, a related form, is given by injection in hospital.
Answers
Theophylline: frequently asked questions
Why does theophylline need blood tests?
Theophylline has a narrow safe range — too little does not help your breathing, and too much causes toxicity such as a racing heartbeat, vomiting and, at high levels, seizures. Blood tests keep the level within a safe target, particularly after any change in dose, brand, smoking or other medicines.
Does smoking affect theophylline?
Yes — smoking speeds up how fast the body breaks theophylline down, so smokers often need more. Importantly, if you stop smoking, your level can rise and you may need less; always tell your doctor if you start or stop smoking so the amount can be adjusted.
Why must I stay on the same brand?
Different modified-release brands release theophylline at different rates, so they are not interchangeable. Switching brands can change your blood level and either reduce the benefit or increase side effects, so you are kept on one named brand unless your doctor changes it deliberately.
What are the warning signs of too much theophylline?
Nausea and vomiting, a fast, pounding or irregular heartbeat, tremor, restlessness, headache and difficulty sleeping can all mean the level is climbing. Report these promptly — at very high levels theophylline can cause seizures, so it is taken seriously.
Authoritative sources
- BNF: Theophylline; Aminophylline.
- electronic Medicines Compendium (SmPC): Theophylline (Uniphyllin Continus).
- NICE NG80: Asthma; NG115: COPD in over 16s.
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