What the FDA labels say about taking them together
Erythromycin and ivacaftor
Ivacaftor's FDA label of March 23, 2026 names erythromycin in its drug interactions section; the erythromycin labels PlainMeds reads (4) do not name ivacaftor. The ivacaftor label: “Therefore, a reduction of the KALYDECO dosage is recommended for patients aged 6 months and older taking concomitant moderate CYP3A inhibitors, such as fluconazole and erythromycin.”
Check it at the source: the erythromycin FDA label on DailyMed (effective August 1, 2024, Teva Pharmaceuticals USA, Inc.); the ivacaftor FDA label on DailyMed (effective March 23, 2026, Vertex Pharmaceuticals Incorporated).
What does the erythromycin label say about ivacaftor?
Erythromycin's label (effective August 1, 2024) and its 3 other brand-application labels do not name ivacaftor in these sections. A label lists what its studies and reports found; it is not a complete list.
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 ivacaftor label say about erythromycin?
Ivacaftor label, drug interactionsTherefore, a reduction of the KALYDECO dosage is recommended for patients aged 6 months and older taking concomitant moderate CYP3A inhibitors, such as fluconazole and erythromycin.
Source: FDA drug label (Kalydeco), Vertex Pharmaceuticals Incorporated, effective March 23, 2026 (SPL set 0ab0c9f8-3eee-4e0f-9f3f-c1e16aaffe25), 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 | Ivacaftor | |
|---|---|---|
| Labeled for | Bacterial infections, Acne | n/a |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $1.96 per tablet 250 mg tablet | n/a |
| 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