What the FDA labels say about taking them together
Foscarnet and quinidine
Foscarnet's FDA label of December 11, 2025 names quinidine in its drug interactions section; the quinidine label PlainMeds reads does not name foscarnet. The foscarnet label: “Abnormal renal function has been observed in clinical practice during the use of FOSCAVIR and ritonavir, or FOSCAVIR, ritonavir, and saquinavir. …”
Check it at the source: the foscarnet FDA label on DailyMed (effective December 11, 2025, Clinigen Limited); the quinidine FDA label on DailyMed (effective February 1, 2018, Sun Pharmaceutical Industries, Inc.).
What does the foscarnet label say about quinidine?
Foscarnet label, drug interactionsAbnormal renal function has been observed in clinical practice during the use of FOSCAVIR and ritonavir, or FOSCAVIR, ritonavir, and saquinavir. (See DOSAGE and ADMINISTRATION. ) Because of the risk of QT prolongation and the potential for torsades de pointes, the use of FOSCAVIR should be avoided in combination with agents known to prolong the QT interval including Class IA (e.g., quinidine or procainamide) or Class III (e.g., dofetilide, amiodarone, sotalol) antiarrhythmic agents, phenothiazines, tricyclic antidepressants, and certain macrolides and fluoroquinolones.
Source: FDA drug label (Foscavir), Clinigen Limited, effective December 11, 2025 (SPL set 90e3da4e-3b1f-428b-99ca-e4bed1c80028), via openFDA; the full label on DailyMed
What does the quinidine label say about foscarnet?
Quinidine's label (effective February 1, 2018) does not name foscarnet in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Quinidine Gluconate), Sun Pharmaceutical Industries, Inc., effective February 1, 2018 (SPL set 5023f053-fcc4-4c2c-aa59-9ec198ad185e), 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
| Foscarnet | Quinidine | |
|---|---|---|
| Labeled for | n/a | Atrial fibrillation |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | n/a | $4.92 per tablet 324 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