Acyclovir Injection and Meperidine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 10, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Meperidine
Acyclovir Injection
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased meperidine and its metabolite normeperidine exposure
Interaction Deep Dive
Concomitant use of acyclovir may increase the plasma concentrations of meperidine and its metabolite, normeperidine. If concomitant use of acyclovir and meperidine is necessary, monitor patients for respiratory depression and sedation at frequent intervals12.
Why it happens (mechanism)
Unknown
Common questions
Can I take Acyclovir Injection and Meperidine together?
Increased meperidine and its metabolite normeperidine exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acyclovir Injection and Meperidine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Acyclovir Injection or Meperidine need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (2)
- Product Information: MEPERGAN intramuscular, intravenous injection, meperidine HCl, promethazine HCl intramuscular, intravenous injection. West-Ward Pharmaceuticals Corp (per FDA), Eatontown, NJ, 2023.
- Product Information: DEMEROL(R) oral tablets, oral solution, meperidine HCl oral tablets, oral solution. Validus Pharmaceuticals LLC (per FDA), Parsippany, NJ, 2023. DailyMed
Keep reading about Meperidine
Keep reading about Acyclovir Injection
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Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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