What the FDA labels say about taking them together
Darunavir and fesoterodine
Darunavir's FDA label of August 29, 2025 names fesoterodine in its drug interactions section; the fesoterodine label PlainMeds reads does not name darunavir. The darunavir label: “When fesoterodine is co-administered with PREZISTA/ritonavir, do not exceed a fesoterodine dose of 4 mg once daily.”
Check it at the source: the darunavir FDA label on DailyMed (effective August 29, 2025, Janssen Products LP); the fesoterodine FDA label on DailyMed (effective April 7, 2026, Pfizer Laboratories Div Pfizer Inc).
What does the darunavir label say about fesoterodine?
Darunavir label, drug interactionsConcomitant Drug Class Drug Name Examples: fesoterodine; Effect on Concentration of Darunavir Or Concomitant Drug: ↑ fesoterodine; Clinical Comment: When fesoterodine is co-administered with PREZISTA/ritonavir, do not exceed a fesoterodine dose of 4 mg once daily.
Source: FDA drug label (PREZISTA), Janssen Products LP, effective August 29, 2025 (SPL set 814301f9-c990-46a5-b481-2879a521a16f), via openFDA; the full label on DailyMed
What does the fesoterodine label say about darunavir?
Fesoterodine's label (effective April 7, 2026) does not name darunavir in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Toviaz), Pfizer Laboratories Div Pfizer Inc, effective April 7, 2026 (SPL set 5be745f0-8ae7-4c3c-9962-37d6263326f1), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Darunavir | Fesoterodine | |
|---|---|---|
| Labeled for | HIV | Overactive bladder |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $1.16 per tablet 600 mg tablet | $0.794 per tablet 4 mg tablet |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once