What the FDA labels say about taking them together
Erythromycin and fentanyl
Fentanyl's FDA label of March 6, 2026 names erythromycin in its drug interactions section; the erythromycin labels PlainMeds reads (4) do not name fentanyl. The fentanyl label: “The concomitant use of Fentanyl Citrate Injection and CYP3A4 inhibitors can increase the plasma concentration of fentanyl, resulting in increased or prolonged opioid effects, particularly when an inhibitor is added …”
Check it at the source: the erythromycin FDA label on DailyMed (effective August 1, 2024, Teva Pharmaceuticals USA, Inc.); the fentanyl FDA label on DailyMed (effective March 6, 2026, Hikma Pharmaceuticals USA Inc.).
What does the erythromycin label say about fentanyl?
Erythromycin's label (effective August 1, 2024) and its 3 other brand-application labels do not name fentanyl 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 fentanyl label say about erythromycin?
Fentanyl label, drug interactionsInhibitors of CYP3A4 Clinical Impact: The concomitant use of Fentanyl Citrate Injection and CYP3A4 inhibitors can increase the plasma concentration of fentanyl, resulting in increased or prolonged opioid effects, particularly when an inhibitor is added after a stable dose of Fentanyl Citrate Injection is achieved. … drug effects are achieved. Monitor for signs of opioid withdrawal. Examples: Macrolide antibiotics (e.g., erythromycin), azole-antifungal agents (e.g., ketoconazole), protease inhibitors (e.g., ritonavir), grapefruit juice
Fentanyl label, warnings and precautionsUse or Discontinuation of Cytochrome P450 3A4 Inhibitors and Inducers Concomitant use of Fentanyl Citrate Injection with a CYP3A4 inhibitor, such as macrolide antibiotics (e.g., erythromycin), azole-antifungal agents (e.g., ketoconazole), and protease inhibitors (e.g., ritonavir), may increase plasma concentrations of fentanyl and prolong opioid adverse reactions, which may exacerbate respiratory depression [see Warnings and Precautions (5.2) ], particularly when an inhibitor is added after a stable dose of Fentanyl Citrate Injection is achieved.
Fentanyl Citrate label (Hospira, Inc., August 24, 2026), drug interactionsMacrolide antibiotics (e.g., erythromycin), azole-antifungal agents (e.g., ketoconazole), protease inhibitors (e.g., ritonavir), grapefruit juice.
Source: FDA drug label (Fentanyl Citrate, NDA019115), Hospira, Inc., effective August 24, 2026 (SPL set bfa8018a-4cbc-434b-e09e-782872b0340a), via openFDA
Source: FDA drug label (Fentanyl Citrate), Hikma Pharmaceuticals USA Inc., effective March 6, 2026 (SPL set ce5db1c2-feb1-4ad2-847a-d02e865bd47e), 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 | Fentanyl | |
|---|---|---|
| Labeled for | Bacterial infections, Acne | Pain |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $1.96 per tablet 250 mg tablet | $1.79 per mL 100 mcg/2 mL vial |
| Shortage now | No current entry | In shortage |
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