Theophylline: what it treats, how to take it, side effects
Last updated September 3, 2026.
Theophylline is a bronchodilator - it relaxes and opens the air passages in the lungs. One of the oldest asthma medicines - and a narrow-window drug: the difference between working and toxic is small, which is why levels get checked and rules get followed.
What does it treat?
Prevention and treatment of wheezing, shortness of breath, and chest tightness from asthma, chronic bronchitis, emphysema, and other lung diseases.
How do you take it?
On the schedule written for you - every 6, 8, 12, or 24 hours depending on the product - with a full glass of water on an empty stomach, at least 1 hour before or 2 hours after a meal. Extended-release tablets: swallow whole, never chew or crush. Exactly as directed: never more, never more often - the blood level is the target, and your doctor checks it on schedule. Illnesses with fever, new medications, quitting smoking, and big diet changes all move the level - any of those earns a call. Missed dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: upset stomach, stomach pain, diarrhea, headache, restlessness, insomnia, and irritability - the caffeine-family feel.
- Serious - call your doctor immediately: vomiting, increased or rapid heart rate, irregular heartbeat, and seizures - the toxicity pattern, and the reason the levels exist.
Who should not take it?
Flag heart-rhythm problems, seizures, ulcers, liver disease, thyroid disease, and high blood pressure. Smoking status matters - tobacco changes how fast the drug clears, so starting or quitting smoking is a dosing event. Caffeine stacks onto the side effects. If you become pregnant, call your doctor.
When is it an emergency?
A seizure, a racing irregular heartbeat, or repeated vomiting on this drug is a 911 call - treat them as possible toxicity, not bad luck. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
Why does this old drug need blood levels?
The window: theophylline's effective range and its toxic range sit close together, and the level moves with fever, infections, new medications, smoking changes, and even diet. The blood tests keep the dose inside the window. The toxicity trio - vomiting, rapid or irregular heartbeat, seizures - is why "feeling fine" never substitutes for the scheduled level.
Why does my smoking status matter?
Tobacco smoke speeds the enzymes that clear theophylline - smokers burn through it faster and get higher doses; quit smoking, and the same dose can climb toxic within days. Vaping and marijuana smoke count too. Any change in smoking - starting, stopping, heavy stretches - is a call-your-doctor event on this drug, not a footnote.
Why empty stomach with water?
Absorption: food - especially big or fatty meals - changes how much drug enters and how fast, and the dose was calibrated against the empty-stomach state. Full glass of water, at least 1 hour before or 2 hours after a meal, same pattern every day. And the extended-release tablets are swallowed whole: chewing one dumps the whole dose at once.
Why is caffeine a problem?
Same family, same effects: coffee, tea, energy drinks, and caffeine pills stack onto theophylline's jitter, insomnia, racing heart, and stomach upset. Moderate habitual caffeine is usually managed into the plan; large or swinging intake is the problem. If the jitters arrive, the caffeine count is the first question your doctor will ask.
How is theophylline different from my inhalers?
Systemic versus local: inhalers deliver drug straight to the airways in micrograms; theophylline is a swallowed whole-body drug - broader reach, broader side effects, and the level-checking that comes with them. Modern practice leads with inhalers; theophylline holds a niche for specific patterns - often nighttime symptoms - or when inhalers alone fall short. If you are on it, there is a reason worth knowing.
What happens if I miss a dose of theophylline?
Take it as soon as you remember, unless it is almost time for the next one - then skip it and never double up. Doubling is the fast route into the toxic window. If you are missing often, tell your doctor - the once-daily formulations exist for exactly that life shape.