Does Acyclovir Interact With Valacyclovir?
4 CONTRAINDICATIONS Valacyclovir tablets are contraindicated in patients who have had a demonstrated clinically significant hypersensitivity reaction [e.g., anaphylaxis, severe cutaneous adverse reactions (SCARs)] to valacyclovir, acyclovir, or any component of the formulation [see Warnings and Precautions (5.4) , Adverse Reactions (6.3) ] .
Severity: Contraindicated
Severity basis: contraindications section (keywords: contraindicated). Combining Acyclovir (Antiviral (nucleoside analogue)) and Valacyclovir (Antiviral (nucleoside analogue)) is classified as a contraindicated interaction.
What to Do
This combination is contraindicated on the FDA label. Do not take these together unless your prescriber explicitly directs it.
How This Interaction Works
Interactions like this one can happen when two medicines have overlapping effects, or when one changes how the other is absorbed, broken down, or cleared from the body. Acyclovir is a antiviral (nucleoside analogue) and Valacyclovir is a antiviral (nucleoside analogue); together they are documented as a contraindicated interaction. How much this matters depends on your dose, your other medications, and your overall health.
If You Take Both Medications
If you have been prescribed both Acyclovir and Valacyclovir, do not start, stop, or change either medication on your own — some medicines are unsafe to stop suddenly. Tell your prescriber and pharmacist that you take both so they can decide whether the combination is right for you, adjust the dose, monitor you more closely, or suggest an alternative.
From the FDA Label
4 CONTRAINDICATIONS Valacyclovir tablets are contraindicated in patients who have had a demonstrated clinically significant hypersensitivity reaction [e.g., anaphylaxis, severe cutaneous adverse reactions (SCARs)] to valacyclovir, acyclovir, or any component of the formulation [see Warnings and Precautions (5.4) , Adverse Reactions (6.3) ] .
Source: FDA structured product labeling (set_id 021ab9d0-7b75-40cf-afde-446942d64388).
Check these against your full medication list in our free Interaction Checker
Frequently Asked Questions
Can you take Acyclovir and Valacyclovir together?
Acyclovir and Valacyclovir have a documented contraindicated interaction. This combination is contraindicated on the FDA label. Do not take these together unless your prescriber explicitly directs it.
How serious is the Acyclovir and Valacyclovir interaction?
It is classified as a contraindicated interaction, based on the FDA label's contraindications section (keywords: contraindicated). A contraindicated pairing generally should not be used together.
What should I do if I'm taking both Acyclovir and Valacyclovir?
If you have been prescribed both Acyclovir and Valacyclovir, do not start, stop, or change either medication on your own — some medicines are unsafe to stop suddenly. Tell your prescriber and pharmacist that you take both so they can decide whether the combination is right for you, adjust the dose, monitor you more closely, or suggest an alternative.
This information is educational — not medical advice.
This page is provided for general educational purposes and summarizes publicly available data from sources such as the U.S. Food & Drug Administration. It is not a substitute for the judgment of a licensed clinician and should not be used to start, stop, or change any medication. It may be incomplete or out of date, and individual circumstances vary. Always talk with your prescriber or pharmacist about your specific medications and health conditions. If you think you may have a medical emergency, call 911.