What the FDA labels say about taking them together
Acyclovir and meperidine
Meperidine's FDA label of November 29, 2025 names acyclovir in its drug interactions section; the acyclovir labels PlainMeds reads (4) do not name meperidine. The meperidine label: “The concomitant use of acyclovir may increase the plasma concentrations of meperidine and its metabolite, normeperidine.”
Check it at the source: the acyclovir FDA label on DailyMed (effective July 24, 2026, Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc.); the meperidine FDA label on DailyMed (effective November 29, 2025, EPIC PHARMA, LLC).
What does the acyclovir label say about meperidine?
Acyclovir's label (effective July 24, 2026) and its 3 other brand-application labels do 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 (ACYCLOVIR), Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc., effective July 24, 2026 (SPL set 0de2f5c7-9e75-4bdf-9c28-e026cc6694b4), via openFDA; the full label on DailyMed
What does the meperidine label say about acyclovir?
Meperidine label, drug interactionsClinical Impact: The concomitant use of acyclovir may increase the plasma concentrations of meperidine and its metabolite, normeperidine. Intervention: If concomitant use of acyclovir and meperidine hydrochloride tablets is necessary, evaluate patients for respiratory depression and sedation at frequent intervals.
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
| Acyclovir | Meperidine | |
|---|---|---|
| Labeled for | Herpes and shingles | Pain |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.0962 per tablet 400 mg tablet | $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