Ketoconazole and Fesoterodine Interaction
Drug interaction information between Ketoconazole and Fesoterodine.
Ketoconazole and Fesoterodine have a documented moderate interaction in FDA labeling.
FDA drug labeling documents a moderate-severity interaction between Ketoconazole and Fesoterodine. This page displays the available source-record category and label text. The category is not an individual risk estimate or medication-combination direction.
How They Interact
Ketoconazole stops your body from breaking down fesoterodine properly, which can double the amount of medicine in your blood.
FDA Label Information
7.2 CYP3A4 Inhibitors Doses of fesoterodine fumarate greater than 4 mg are not recommended in adult patients taking strong CYP3A4 inhibitors, such as ketoconazole, itraconazole, and clarithromycin [see Dosage and Administration (2.5) ] . In a study in adults, co-administration of the strong CYP3A4 inhibitor ketoconazole with fesoterodine led to approximately a doubling of the maximum concentration (C max ) and area under the concentration versus time curve (AUC) of 5-hydroxymethyl tolterodine (5-HMT), the active metabolite of fesoterodine. Compared with CYP2D6 extensive metabolizers not...
Ketoconazole Also Interacts With
- Alfuzosin major
- Dronedarone major
- Ranolazine major
- Saxagliptin major
- Sildenafil major
Fesoterodine Also Interacts With
- Darunavir major
- Itraconazole major
- Clarithromycin moderate
- Estradiol minor
- Diltiazem minor
Frequently Asked Questions
What SPL severity band is on file for Ketoconazole + Fesoterodine?
Compiled FDA labeling labels this pair moderate. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Ketoconazole has 113 labeled pairs on file vs Fesoterodine's 15. In the moderate band specifically: Ketoconazole has 22 (also Alprazolam, Aprepitant, Budesonide/Formoterol, Dexamethasone); Fesoterodine has 2 (also Clarithromycin).
What mechanism field is on file for Ketoconazole and Fesoterodine?
Ketoconazole stops your body from breaking down fesoterodine properly, which can double the amount of medicine in your blood.
Ketoconazole carries more major-labeled pairs than Fesoterodine
SPL source-record counts only. This page's band is moderate · classes on file: Ketoconazole (Azole Antifungal); Fesoterodine (Anticholinergic (Overactive Bladder)).
Ketoconazole has 6 major-labeled pairs vs Fesoterodine's 2. This page itself is in the moderate band, not the major band.
6 major · 22 moderate · 85 minor · 113 total
- Other moderate peers for Ketoconazole
- Alprazolam
- Aprepitant
- Budesonide/Formoterol
- Dexamethasone
2 major · 2 moderate · 11 minor · 15 total
- Other moderate peers for Fesoterodine
- Clarithromycin
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. This registry does not provide individual medication-combination directions.
Read our methodology - how this data is sourced, computed, and verified.