What the FDA labels say about taking them together
Enzalutamide and fostemsavir
Fostemsavir's FDA label of February 13, 2024 names enzalutamide in its contraindications section; the enzalutamide labels PlainMeds reads (2) do not name fostemsavir. The fostemsavir label: “Coadministration is contraindicated due to potential for loss of therapeutic effect to RUKOBIA.”
Check it at the source: the enzalutamide FDA label on DailyMed (effective July 28, 2026, Astellas Pharma US, Inc.); the fostemsavir FDA label on DailyMed (effective February 13, 2024, ViiV Healthcare Company).
What does the enzalutamide label say about fostemsavir?
Enzalutamide's label (effective July 28, 2026) and its 1 other brand-application label do not name fostemsavir in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Xtandi), Astellas Pharma US, Inc., effective July 28, 2026 (SPL set b129fdc9-1d8e-425c-a5a9-8a2ed36dfbdf), via openFDA; the full label on DailyMed
What does the fostemsavir label say about enzalutamide?
Fostemsavir label, contraindicationsEnzalutamide o Anticonvulsants: Carbamazepine, phenytoin o Antimycobacterial: Rifampin o Antineoplastic:
Fostemsavir label, drug interactionsConcomitant Drug Class/Drug Name: Androgen receptor inhibitor: Enzalutamide; Effect on Concentration of Temsavir and/or Concomitant Drug: ↓Temsavir; Clinical Comment: Coadministration is contraindicated due to potential for loss of therapeutic effect to RUKOBIA [see Contraindications ()].
Source: FDA drug label (Rukobia), ViiV Healthcare Company, effective February 13, 2024 (SPL set a21006b7-6d6f-4f06-81b4-17978756452b), 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
| Enzalutamide | Fostemsavir | |
|---|---|---|
| Labeled for | Prostate cancer | HIV |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $156.84 per tablet 600 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