What the FDA labels say about taking them together
Digoxin and quinidine
Digoxin's FDA label (Lanoxin) of October 17, 2025 names quinidine in its drug interactions section, and quinidine's label names digoxin too. The quinidine label: “Altered pharmacokinetics of other drugs: Quinidine slows the elimination of digoxin and simultaneously reduces digoxin's apparent volume of distribution.”
Check it at the source: the digoxin FDA label on DailyMed (effective December 5, 2024, Advanz Pharma (US) Corp.); the quinidine FDA label on DailyMed (effective February 1, 2018, Sun Pharmaceutical Industries, Inc.).
What does the digoxin label say about quinidine?
Lanoxin label (Covis Pharma US, Inc, October 17, 2025), drug interactionsQuinidine; NA; 54-83%; Measure serum digoxin concentrations before initiating concomitant drugs. Reduce digoxin concentrations by decreasing dose by approximately 30-50% or by modifying the dosing frequency and continue monitoring.
Source: FDA drug label (Lanoxin, NDA009330), Covis Pharma US, Inc, effective October 17, 2025 (SPL set 9ec84cac-6ecc-43dc-8006-6ccc029e2707), via openFDA
Source: FDA drug label (LANOXIN), Advanz Pharma (US) Corp., effective December 5, 2024 (SPL set d91e3646-4c63-4512-ab22-db39c085c4dc), via openFDA; the full label on DailyMed
What does the quinidine label say about digoxin?
Quinidine label, drug interactionsAltered pharmacokinetics of other drugs: Quinidine slows the elimination of digoxin and simultaneously reduces digoxin's apparent volume of distribution.
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
| Digoxin | Quinidine | |
|---|---|---|
| Labeled for | Heart failure, Atrial fibrillation | Atrial fibrillation |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.133 per tablet 125 mcg tablet | $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