Theophylline
A methylxanthine bronchodilator for chronic asthma and COPD, with a narrow therapeutic range and many drug interactions.
Drug card
- Class
- Methylxanthine
- How it works
- Inhibiting phosphodiesterases and blocking adenosine receptors in the airways
- Used for
- Chronic asthma
- COPD: chronic bronchitis and emphysema
- Known for
- Nausea and vomiting
- Arrhythmias at high blood levels
- Seizures at high blood levels
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does theophylline work?
A xanthine alkaloid also found in tea and coffee. It relaxes bronchial smooth muscle, probably by inhibiting PDE III and, less so, PDE IV, and it blocks adenosine receptors; it also strengthens diaphragm contraction. The liver clears it, mainly by CYP1A2, so many drugs, smoking and illness change its blood levels.
Uses
What is theophylline used for?
- Chronic asthma
- COPD: chronic bronchitis and emphysema
Side effects
Side effects of theophylline
- Nausea and vomitingKnown for
- Arrhythmias at high blood levelsKnown forSerious
- Seizures at high blood levelsKnown forSerious
- Headache
- Insomnia
- Irritability and restlessness
- Shaky hands (tremor)
- Fast heartbeat and palpitations
- Acid reflux and stomach irritation
- Passing more urine (diuresis)
- Low potassium in toxicitySerious
- Raised blood sugar
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- The useful and toxic blood levels lie close together, so serum levels are measured, especially after any change.
- Cimetidine, ciprofloxacin, erythromycin, clarithromycin and fluvoxamine raise levels; so does stopping smoking.
- Rifampicin, phenytoin, St John's wort and carbamazepine lower its levels.
- Care in peptic ulcer, seizure disorders and arrhythmias, which it can worsen.
Good to know: It adds little to inhaled beta-2 agonists and steroids in an acute attack, and persistent vomiting can be the first sign of toxicity.
Remember it
A way to remember it
A cousin of caffeine with a narrow margin.
Its everyday side effects are caffeine-like (nausea, headache, insomnia, restlessness), and because toxic levels sit close to useful ones, high levels bring arrhythmias and seizures.
Written for biofideX
Its class
Methylxanthines
Methylxanthines such as theophylline relax bronchial smooth muscle, probably by inhibiting phosphodiesterase enzymes (PDE III and, less so, PDE IV), and they block adenosine receptors. They also stimulate the brain and heart, strengthen diaphragm contraction and increase urine flow. Their protective, anti-inflammatory effect on the airways comes through other mechanisms that are not well understood.
Easily mixed up with PDE5 inhibitors and short-acting beta-2 agonists.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Lungs and allergy
Theophylline is one of 16 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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