What the FDA labels say about taking them together
Acyclovir and valacyclovir
Acyclovir's FDA label of July 24, 2026 names valacyclovir in its contraindications section, and valacyclovir's label names acyclovir too. The acyclovir label: “CONTRAINDICATIONS AVACLYR is contraindicated for patients who develop sensitivity to acyclovir or valacyclovir.”
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 valacyclovir FDA label on DailyMed (effective November 12, 2025, GlaxoSmithKline LLC).
What does the acyclovir label say about valacyclovir?
Acyclovir label, contraindicationsCONTRAINDICATIONS Acyclovir is contraindicated in patients who have had a demonstrated clinically significant hypersensitivity reaction [e.g., anaphylaxis, severe cutaneous adverse reactions (SCARs)] to acyclovir, valacyclovir, or any component of the formulation (see WARNINGS and ADVERSE REACTIONS ).
Acyclovir label, warningsAcyclovir is contraindicated in patients who have developed SCARs with the use of acyclovir or valacyclovir, or any component of the formulation (see CONTRAINDICATIONS and ADVERSE REACTIONS ).
Zovirax label (Bausch Health US, LLC, February 1, 2021), contraindicationsCONTRAINDICATIONS ZOVIRAX Cream is contraindicated in patients with known hypersensitivity to acyclovir, valacyclovir, or any component of the formulation.
Avaclyr label (Fera Pharmaceuticals, LLC, January 5, 2026), contraindicationsCONTRAINDICATIONS AVACLYR is contraindicated for patients who develop sensitivity to acyclovir or valacyclovir.
Source: FDA drug label (Zovirax, NDA021478), Bausch Health US, LLC, effective February 1, 2021 (SPL set 125dbe4e-94ba-45bd-a714-f9c4b8e8b5c2), via openFDA
Source: FDA drug label (Avaclyr, NDA202408), Fera Pharmaceuticals, LLC, effective January 5, 2026 (SPL set 3ce26231-bc40-48b0-85e5-2e7622f334d7), via openFDA
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 valacyclovir label say about acyclovir?
Valacyclovir label, contraindicationsCONTRAINDICATIONS VALTREX is 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 )].
Valacyclovir label, warnings and precautionsPrecipitation of acyclovir in renal tubules may occur when the solubility (2.5 mg/mL) is exceeded in the intratubular fluid.
Source: FDA drug label (VALTREX), GlaxoSmithKline LLC, effective November 12, 2025 (SPL set f8e0d8f8-cb73-4206-a484-88f5c4fbd719), 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 | Valacyclovir | |
|---|---|---|
| Labeled for | Herpes and shingles | Herpes and shingles |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.0962 per tablet 400 mg tablet | $0.229 per tablet 500 mg tablet |
| Shortage now | No current entry | No current entry |
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