Theophylline
- Class: Bronchodilator
- Used for: asthma and COPD
- Say it: thee-OFF-ih-lin
- Forms: tablet, capsule, oral liquid
THEOPHYLLINE comes from TEA — and like far too much strong tea, an overdose leaves you shaking, vomiting and racing.
It is a caffeine relative, and the etymology is real. The therapeutic range is narrow, so toxicity looks exactly like too much coffee, then turns into arrhythmia and seizures.
It inhibits phosphodiesterase and blocks adenosine receptors, relaxing the airway. The therapeutic range is roughly 10-20 mg/L, and above it come vomiting, arrhythmias and seizures — so levels are checked, not guessed.
Side effects
Common: nausea, insomnia, headache
Serious: arrhythmia, seizures
Typical dose
300–600 mg daily as modified-release
Dosed to a blood level rather than to a fixed milligram amount. Modified-release brands are not interchangeable — switching brand means re-checking the level.
Check yourself
A patient on theophylline becomes toxic after starting ciprofloxacin. Why?
- Ciprofloxacin inhibits CYP1A2, the enzyme that clears theophylline
- The two drugs bind the same airway receptor
- Ciprofloxacin reduces renal excretion of theophylline
- The infection itself raises theophylline levels
Show answer
A. Ciprofloxacin inhibits CYP1A2, the enzyme that clears theophylline
Theophylline has a narrow therapeutic range, so anything slowing its metabolism pushes it over. CYP1A2 inhibitors — ciprofloxacin, erythromycin, cimetidine — and stopping smoking all do exactly that.
See it, don't memorize it
The app has the mechanism comic and a patient case for Theophylline – plus the name link, the class mnemonic, pronunciation you can hear, and a self-check, for the top 100 drugs. One purchase, no subscription, no account.