No dosing adjustments are recommended in the presence of moderate CYP3A4 inhibitors (e.g., erythromycin, fluconazole, diltiazem, verapamil and grapefruit juice).
Source: FDA drug label - fesoterodine fumarate
Fesoterodine Fumarate Interactions
Brand names: Fesoterodine Fumarate
5 interactions on record
Following blockade of CYP3A4 by coadministration of the moderate CYP3A4 inhibitor fluconazole 200 mg twice a day for 2 days, the average (90% confidence interval) increase in C max and AUC of the active metabolite of fesoterodine was approximately 19% (11% to 28%) and 27% (18% to 36%) respectively. No dosing adjustments are recommended in the presence of moderate CYP3A4 inhibitors (e.g., erythromycin, fluconazole, diltiazem, verapamil and grapefruit juice).
Source: FDA drug label - fesoterodine fumarate
7.2 CYP3A4 Inhibitors Doses of fesoterodine fumarate extended-release tablets 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 )].
Source: FDA drug label - fesoterodine fumarate
7.2 CYP3A4 Inhibitors Doses of fesoterodine fumarate extended-release tablets 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 )].
Source: FDA drug label - fesoterodine fumarate
7.2 CYP3A4 Inhibitors Doses of fesoterodine fumarate extended-release tablets 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, coadministration 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 taking ketoconazole, further increases in the exposure to 5-HMT were observed in subjects who were CYP2D6 poor metabolizers taking ketoconazole [see Clinical Pharmacology ( 12.3 )].
Source: FDA drug label - fesoterodine fumarate