What the FDA labels say about taking them together
Erythromycin and quinidine
Erythromycin's FDA label of August 1, 2024 names quinidine in its drug interactions section; the quinidine label PlainMeds reads does not name erythromycin. The erythromycin label: “… cyclosporine, tacrolimus, alfentanil, disopyramide, bromocriptine, rifabutin, quinidine methylprednisolone, cilostazol, and vinblastine.”
Check it at the source: the erythromycin FDA label on DailyMed (effective August 1, 2024, Teva Pharmaceuticals USA, Inc.); the quinidine FDA label on DailyMed (effective February 1, 2018, Sun Pharmaceutical Industries, Inc.).
What does the erythromycin label say about quinidine?
Erythromycin label, drug interactionsThere have been spontaneous or published reports of CYP3A based interactions of erythromycin with cyclosporine, carbamazepine, tacrolimus, alfentanil, disopyramide, rifabutin, quinidine, methyl-prednisolone, cilostazol, vinblastine, and bromocriptine.
Erythromycin label, warningsErythromycin should be avoided in patients with known prolongation of 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.
Ery-Ped label (Azurity Pharmaceuticals, Inc. (formerly Arbor Pharmaceuticals), December 16, 2023), drug interactionsReduction of sildenafil dosage should be considered. (See Viagra package insert.) There have been spontaneous or published reports of CYP3A based interactions of erythromycin with cyclosporine, carbamazepine, tacrolimus, alfentanil, disopyramide, rifabutin, quinidine, methylprednisolone, cilostazol, vinblastine, and bromocriptine.
Erythromycin label (Dr. Reddy's Labratories Inc., September 25, 2025), drug interactionsReduction of sildenafil dosage should be considered. (See Viagra package insert.) There have been spontaneous or published reports of CYP3A based interactions of erythromycin with carbamazepine, cyclosporine, tacrolimus, alfentanil, disopyramide, bromocriptine, rifabutin, quinidine methylprednisolone, cilostazol, and vinblastine.
Source: FDA drug label (Ery-Ped, NDA050207), Azurity Pharmaceuticals, Inc. (formerly Arbor Pharmaceuticals), effective December 16, 2023 (SPL set 04775721-ab87-4b66-808c-d67a21032385), via openFDA
Source: FDA drug label (Erythromycin, NDA050536), Dr. Reddy's Labratories Inc., effective September 25, 2025 (SPL set a2dcb48a-212c-1b0c-ec35-ee2ade85847f), via openFDA
Source: FDA drug label (Erythromycin), Teva Pharmaceuticals USA, Inc., effective August 1, 2024 (SPL set 75a0bd5a-d09f-483b-bfd8-f8343b149eb2), via openFDA; the full label on DailyMed
What does the quinidine label say about erythromycin?
Quinidine's label (effective February 1, 2018) does not name erythromycin 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
| Erythromycin | Quinidine | |
|---|---|---|
| Labeled for | Bacterial infections, Acne | Atrial fibrillation |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $1.96 per tablet 250 mg 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