What the FDA labels say about taking them together
Meperidine and ritonavir
Meperidine's FDA label of November 29, 2025 names ritonavir in its drug interactions section, and ritonavir's label names meperidine too. The meperidine label: “The concomitant use of DEMEROL Injection 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 meperidine FDA label on DailyMed (effective November 29, 2025, EPIC PHARMA, LLC); the ritonavir FDA label on DailyMed (effective July 23, 2026, AbbVie Inc.).
What does the meperidine label say about ritonavir?
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 … 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
What does the ritonavir label say about meperidine?
Ritonavir label, drug interactionsConcomitant Drug Class/Drug Name: Anesthetic: meperidine; Effect on Concentration of Ritonavir or Concomitant Drug: ↓ meperidine/ ↑ normeperidine (metabolite); Clinical Comment: Dosage increase and long-term use of meperidine with ritonavir are not recommended due to the increased concentrations of the metabolite normeperidine which has both analgesic activity and CNS stimulant activity (e.g., seizures).
Source: FDA drug label (Norvir), AbbVie Inc., effective July 23, 2026 (SPL set 2849298e-de6e-47bb-8194-56e075b33fc3), 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.
Which combination products and biosimilars carry the same label text?
Their labels quote the same sentences for their ingredient; each has its own page with its own label dates.
Both medicines on the record
| Meperidine | Ritonavir | |
|---|---|---|
| Labeled for | Pain | HIV |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.157 per mL 50 mg/5 mL solution | $0.607 per tablet 100 mg tablet |
| Shortage now | Listed; available | A presentation being discontinued |
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