Tolterodine and Fluoxetine Interaction
Drug interaction information between Tolterodine and Fluoxetine.
Tolterodine and Fluoxetine have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Tolterodine and Fluoxetine. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Fluoxetine slows down the process your body uses to get rid of tolterodine, leading to higher levels of the drug in your blood.
What To Do
Even though drug levels increase, your doctor does not need to change your dose when these are used together.
FDA Label Information
( 7.6 ) 7.1 Potent CYP2D6 Inhibitors Fluoxetine, a potent inhibitor of CYP2D6 activity, significantly inhibited the metabolism of tolterodine immediate release in CYP2D6 extensive metabolizers, resulting in a 4.8-fold increase in tolterodine AUC. No dose adjustment is required when tolterodine and fluoxetine are co-administered [see Clinical Pharmacology (12.3) ] . Drug Interactions Potent CYP2D6 Inhibitors Fluoxetine is a selective serotonin reuptake inhibitor and a potent inhibitor of CYP2D6 activity.
Tolterodine Also Interacts With
- Clarithromycin moderate
- Omeprazole minor
- Hydrochlorothiazide minor
- Furosemide minor
- Estradiol minor
Fluoxetine Also Interacts With
- Aspirin major
- Warfarin major
- Olanzapine major
- Pimozide major
- Thioridazine major
Frequently Asked Questions
Can I take Tolterodine and Fluoxetine together?
This is a minor interaction. Even though drug levels increase, your doctor does not need to change your dose when these are used together.
How serious is the interaction between Tolterodine and Fluoxetine?
This interaction is classified as "minor" severity by the FDA. Minor interactions are unlikely to cause significant problems but should still be mentioned to your healthcare provider.
Why do Tolterodine and Fluoxetine interact?
Fluoxetine slows down the process your body uses to get rid of tolterodine, leading to higher levels of the drug in your blood.
Understanding the Tolterodine and Fluoxetine Interaction
FDA-approved prescribing information for these two drugs flags their combination as a minor-severity interaction. Tolterodine belongs to the Anticholinergic (Overactive Bladder) class and Fluoxetine belongs to the Selective Serotonin Reuptake Inhibitor (SSRI) class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Fluoxetine slows down the process your body uses to get rid of tolterodine, leading to higher levels of the drug in your blood. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Tolterodine has 15 total documented interactions on file in this dataset, and Fluoxetine has 68. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Even though drug levels increase, your doctor does not need to change your dose when these are used together. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Tolterodine or Fluoxetine based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.