What the FDA labels say about taking them together
Ketoconazole and meperidine
Meperidine's FDA label of November 29, 2025 names ketoconazole in its drug interactions section; the ketoconazole label PlainMeds reads does not name meperidine. The meperidine label: “The concomitant use of meperidine hydrochloride tablets and CYP3A4 or CYP2B6 inhibitors can increase the plasma concentration of meperidine, resulting in increased or prolonged opioid effects. …”
Check it at the source: the ketoconazole FDA label on DailyMed (effective January 28, 2026, E. Fougera & Co. a division of Fougera Pharmaceuticals, LLC); the meperidine FDA label on DailyMed (effective November 29, 2025, EPIC PHARMA, LLC).
What does the ketoconazole label say about meperidine?
Ketoconazole's label (effective January 28, 2026) does not name meperidine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (ketoconazole), E. Fougera & Co. a division of Fougera Pharmaceuticals, LLC, effective January 28, 2026 (SPL set cad7c647-34a9-4e4e-83b3-8d78e58f588f), via openFDA; the full label on DailyMed
What does the meperidine label say about ketoconazole?
Meperidine label, drug interactionsInhibitors of CYP3A4 and CYP2B6 Clinical Impact: The concomitant use of meperidine hydrochloride tablets and CYP3A4 or CYP2B6 inhibitors can increase the plasma concentration of meperidine, resulting in increased or prolonged opioid effects. These effects could be more pronounced with concomitant use of meperidine hydrochloride tablets and CYP2B6 and CYP3A4 inhibitors … opioid withdrawal. Examples: Macrolide antibiotics (e.g., erythromycin), azole-antifungal agents (e.g., ketoconazole), protease inhibitors (e.g., ritonavir)
Meperidine label, warnings and precautionsUse or Discontinuation of Cytochrome P450 3A4 (CYP3A4) Inhibitors and Inducers Concomitant use of meperidine hydrochloride tablets 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 meperidine and prolong opioid adverse reactions, which may cause potentially fatal respiratory depression, particularly when an inhibitor is added after a stable dose of meperidine hydrochloride tablets is achieved.
Source: FDA drug label (Demerol, NDA021171), Hospira, Inc., effective July 20, 2026 (SPL set b31d1308-28c3-43f4-e0a6-2f3ed76b8975), via openFDA
Source: FDA drug label (Meperidine Hydrochloride), EPIC PHARMA, LLC, effective November 29, 2025 (SPL set fae5cc34-5917-4445-9516-25f97ffca8db), 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
| Ketoconazole | Meperidine | |
|---|---|---|
| Labeled for | Fungal infections | Pain |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.249 per gram 2% cream | $0.157 per mL 50 mg/5 mL solution |
| Shortage now | No current entry | Listed; available |
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