What the FDA labels say about taking them together
Azithromycin and quinidine
Azithromycin's FDA label of December 4, 2025 names quinidine in its warnings and precautions section; the quinidine label PlainMeds reads does not name azithromycin. The azithromycin label: “… hypomagnesemia, clinically significant bradycardia, and in patients receiving Class IA (quinidine, procainamide) or Class III antiarrhythmic agents.”
Check it at the source: the azithromycin FDA label on DailyMed (effective December 4, 2025, Bionpharma Inc.); the quinidine FDA label on DailyMed (effective February 1, 2018, Sun Pharmaceutical Industries, Inc.).
What does the azithromycin label say about quinidine?
Azithromycin label, warnings and precautionsProviders should consider the risk of QT prolongation which can be fatal when weighing the risks and benefits of azithromycin for at-risk groups including: patients with known prolongation of the QT interval, a history of torsades de pointes, congenital long QT syndrome, bradyarrhythmias or uncompensated heart failure patients on drugs known to prolong the QT interval patients with ongoing proarrhythmic conditions such as uncorrected hypokalemia or hypomagnesemia, clinically significant bradycardia, and in patients receiving Class IA (quinidine, procainamide) or Class III (dofetilide, amiodarone, sotalol) antiarrhythmic agents.
Zithromax label (Pfizer Laboratories Div Pfizer Inc, July 24, 2026), warnings and precautionspatients with ongoing proarrhythmic conditions such as uncorrected hypokalemia or hypomagnesemia, clinically significant bradycardia, and in patients receiving Class IA (quinidine, procainamide) or Class III (dofetilide, amiodarone, sotalol) antiarrhythmic agents.
Source: FDA drug label (Zithromax, NDA050711), Pfizer Laboratories Div Pfizer Inc, effective July 24, 2026 (SPL set db52b91e-79f7-4cc1-9564-f2eee8e31c45), via openFDA
Source: FDA drug label (Azithromycin), Bionpharma Inc., effective December 4, 2025 (SPL set 859bb02c-a4bc-46fa-9fc9-def1219b5dfb), via openFDA; the full label on DailyMed
What does the quinidine label say about azithromycin?
Quinidine's label (effective February 1, 2018) does not name azithromycin 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
| Azithromycin | Quinidine | |
|---|---|---|
| Labeled for | Bacterial infections | Atrial fibrillation |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.266 per tablet 250 mg tablet | $4.92 per tablet 324 mg tablet |
| Shortage now | A presentation being discontinued | 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