Felodipine and Theophylline: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Theophylline
Felodipine
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
A decrease of theophylline efficacy
Interaction Deep Dive
Felodipine reduced the theophylline area under the plasma concentration-time curve (AUC) by 18.3% in ten healthy volunteers1. Theophylline aminopropanol 200 mg (equivalent to 141 mg anhydrous theophylline) was given orally three times daily alone and in combination with felodipine 5 mg three times daily. The clinical importance of this interaction has not been determined.
Why it happens (mechanism)
Unknown
Common questions
Can I take Felodipine and Theophylline together?
A decrease of theophylline efficacy Always confirm with your pharmacist or prescriber before making any change.
How serious is the Felodipine and Theophylline interaction?
It is rated minor. Usually limited clinical impact.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Felodipine or Theophylline need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (1)
- Bratel T, Billing B, & Dahlqvist R: Felodipine reduces the absorption of theophylline in man. Eur J Clin Pharmacol 1989; 36:481-485. PubMed
Keep reading about Theophylline
Keep reading about Felodipine
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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