What the FDA labels say about taking them together
Dofetilide and erythromycin
Erythromycin's FDA label of August 1, 2024 names dofetilide in its warnings section; dofetilide's label does not name erythromycin itself but warns about its class (macrolides). The erythromycin label: “Erythromycin 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 …”
Check it at the source: the dofetilide FDA label on DailyMed (effective April 21, 2026, Pfizer Laboratories Div Pfizer Inc); the erythromycin FDA label on DailyMed (effective August 1, 2024, Teva Pharmaceuticals USA, Inc.).
What does the dofetilide label say about erythromycin?
Dofetilide's label does not name erythromycin itself; it warns about its class (macrolides):
Dofetilide label, warningsUse with Drugs that Prolong QT Interval and Antiarrhythmic Agents The use of TIKOSYN in conjunction with other drugs that prolong the QT interval has not been studied and is not recommended. Such drugs include phenothiazines, cisapride, bepridil, tricyclic antidepressants, certain oral macrolides, and certain fluoroquinolones.
Source: FDA drug label (Tikosyn), Pfizer Laboratories Div Pfizer Inc, effective April 21, 2026 (SPL set 02438044-d6a3-49e9-a1ac-3aad21ef2c8c), via openFDA; the full label on DailyMed
What does the erythromycin label say about dofetilide?
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.
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
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
| Dofetilide | Erythromycin | |
|---|---|---|
| Labeled for | Atrial fibrillation | Bacterial infections, Acne |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.203 per capsule 125 mcg capsule | $1.96 per tablet 250 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