Respiratory
Theophylline
Aminophylline (intravenous form) — An older oral bronchodilator now used selectively because of its narrow safety margin.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
Theophylline is an oral bronchodilator used as an add-on in asthma and COPD when inhaled treatments are not enough. Its intravenous form, aminophylline, is used in hospital for severe attacks.
How it works
It relaxes airway smooth muscle and has mild anti-inflammatory effects, easing airflow obstruction. It acts through several mechanisms inside cells; the same widespread actions on the heart and nervous system are why excess causes palpitations, agitation and seizures.
In practice
In practice theophylline has moved down the treatment ladder precisely because it is difficult to use safely: it has a narrow therapeutic range, so blood levels are monitored, and many everyday factors shift those levels. Illness, heart failure, liver disease and a number of common drugs — some antibiotics (such as ciprofloxacin and clarithromycin) and others — raise levels towards toxicity, while smoking lowers them, meaning a level can swing dangerously if someone stops smoking. Different brands are not interchangeable, so the same preparation is kept. Toxicity shows as nausea and vomiting, agitation, a fast or irregular heartbeat and, at the extreme, seizures and serious arrhythmias. Because of all this it is generally reserved for when inhaled therapies are insufficient.
Examples
Practical use
How to take it & use it well
- Take theophylline at the same times each day, and try to keep the timing consistent in relation to food, as this affects how the medicine is absorbed.
- Swallow modified-release tablets or capsules whole with water unless your pharmacist confirms they can be opened; do not crush or chew them.
- Stick to one brand of theophylline whenever possible, because different brands can release the drug differently and change the level in your blood.
- Attend any blood tests your team arranges to check your theophylline level, since the safe range is narrow and tests guide the right amount for you.
- Tell your prescriber if you start or stop smoking, as this can change how quickly your body clears the drug and may need a dose review.
- Do not double up if you miss a dose; take the next one as planned and ask your pharmacist if you are unsure.
Common uses
- Add-on therapy in asthma or COPD
- Severe acute asthma in hospital (intravenous aminophylline)
Monitoring
- Theophylline blood level (and after dose, brand, smoking or interacting-drug changes)
- Heart rate/rhythm and symptoms
- Potassium with intravenous use
Weighing it up
Advantages & disadvantages
Advantages
- Helps open the airways and ease breathing in some people with asthma or chronic obstructive pulmonary disease who need extra control.
- Can be useful as an add-on when inhalers alone are not giving enough symptom relief.
- Available as long-acting forms that allow steady levels across the day with regular dosing.
- Has a long history of use, so its effects and monitoring needs are well understood by NHS teams.
Disadvantages
- Has a narrow margin between a helpful level and a harmful one, so careful monitoring is needed.
- Side effects such as nausea, headache, a fast or irregular heartbeat, restlessness and tremor can signal that levels are too high.
- Many common factors, including infections, smoking changes and other medicines, can shift blood levels and require dose adjustment.
- Switching between brands without your team's knowledge can lead to under-treatment or toxicity.
Key safety principles
What to watch for
- Narrow therapeutic range — levels are monitored; toxicity causes nausea, palpitations, agitation, arrhythmias and seizures.
- Many interactions — some antibiotics and other drugs raise levels; smoking (and stopping smoking) changes them.
- Brands are not interchangeable — keep the same preparation.
Key interactions
What to avoid or check alongside
- Certain antibiotics such as ciprofloxacin and clarithromycin can raise theophylline levels and increase the risk of toxicity.
- Some antifungals like fluconazole can also increase theophylline levels, so your team may check a blood level.
- Smoking and some anti-epileptic medicines such as carbamazepine and phenytoin can lower theophylline levels and reduce its effect.
- Combining theophylline with other stimulant medicines or large amounts of caffeine can worsen side effects like a racing heart and jitteriness.
- Certain heart-rhythm and stomach-acid medicines can alter theophylline levels, so always check new medicines with your pharmacist.
Patient & carer advice
- Stay on the same brand and attend your blood tests
- Tell us if you start or stop smoking, or start new medicines or antibiotics
- Report palpitations, persistent nausea, headache or feeling agitated
Use with
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Answers
Theophylline: frequently asked questions
Why do I need blood tests on theophylline?
Theophylline has only a small gap between a helpful level and a harmful one. Blood tests let your team confirm the level is in the safe range and adjust your dose if needed.
Does smoking affect theophylline?
Yes. Smoking speeds up how your body clears theophylline, so smokers often need more. If you stop smoking, levels can rise and your dose may need to be reduced, so tell your prescriber.
Can I switch between different brands of theophylline?
It is best to stay on the same brand. Different brands can release the drug at different rates, which can change your blood level and lead to too little effect or to side effects.
What are signs that my theophylline level is too high?
Warning signs include feeling sick, vomiting, a fast or irregular heartbeat, tremor, restlessness and headache. If you notice these, contact your team promptly as your level may need checking.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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