Oxybutynin and Ketoconazole Interaction
Drug interaction information between Oxybutynin and Ketoconazole.
Oxybutynin and Ketoconazole have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Oxybutynin and Ketoconazole. 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
Ketoconazole blocks the enzyme that breaks down oxybutynin, which can cause the amount of oxybutynin in your body to double.
What To Do
Your doctor may need to lower your dose of oxybutynin and monitor you closely for side effects.
FDA Label Information
Mean oxybutynin chloride plasma concentrations were approximately 2 fold higher when Oxybutynin chloride extended-release tablets were administered with ketoconazole, a potent CYP3A4 inhibitor. (7) Co-administration with strong cytochrome P450 (CYP) 3A4 inhibitors (e.g., ketoconazole) increases the systemic exposure of oxybutynin.
Oxybutynin Also Interacts With
- Erythromycin minor
- Clarithromycin minor
- Itraconazole minor
- Metoclopramide minor
- Carbamazepine minor
Ketoconazole Also Interacts With
- Alfuzosin major
- Dronedarone major
- Ranolazine major
- Saxagliptin major
- Sildenafil major
Frequently Asked Questions
Can I take Oxybutynin and Ketoconazole together?
This is a minor interaction. Your doctor may need to lower your dose of oxybutynin and monitor you closely for side effects.
How serious is the interaction between Oxybutynin and Ketoconazole?
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 Oxybutynin and Ketoconazole interact?
Ketoconazole blocks the enzyme that breaks down oxybutynin, which can cause the amount of oxybutynin in your body to double.
Understanding the Oxybutynin and Ketoconazole Interaction
FDA-approved prescribing information for these two drugs flags their combination as a minor-severity interaction. Oxybutynin belongs to the Anticholinergic / Antispasmodic class and Ketoconazole belongs to the Azole Antifungal class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Ketoconazole blocks the enzyme that breaks down oxybutynin, which can cause the amount of oxybutynin in your body to double. 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. Oxybutynin has 7 total documented interactions on file in this dataset, and Ketoconazole has 113. 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: Your doctor may need to lower your dose of oxybutynin and monitor you closely for side effects. 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 Oxybutynin or Ketoconazole 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.