Valacyclovir vs Acyclovir
Valacyclovir (Valtrex) is a prodrug of acyclovir (Zovirax): once in the body it converts to the same active drug. The practical difference is convenience, since valacyclovir is absorbed better and taken far less often.
Antiviral (nucleoside analogue prodrug)
Antiviral (nucleoside analogue)
A prodrug of acyclovir with better absorption, so it can be dosed just once or twice a day for herpes, cold sores, and shingles.
The original herpes antiviral — highly effective and inexpensive, but usually taken multiple times a day because of lower absorption.
Herpes / cold sores / shingles
Herpes / cold sores / shingles
- Genital herpes (treatment and suppression)
- Cold sores (herpes labialis)
- Shingles (herpes zoster)
- Chickenpox in children
- Genital herpes (treatment and suppression)
- Cold sores (herpes labialis)
- Shingles (herpes zoster)
- Chickenpox (varicella)
- Genital herpes, initial episode: 1 g twice daily for 7–10 days
- Genital herpes, recurrent: 500 mg twice daily for 3 days
- Genital herpes, suppression: 500 mg–1 g once daily
- Cold sores: 2 g twice daily for one day
- Shingles: 1 g three times daily for 7 days
- Genital herpes, initial episode: 200 mg five times daily for 10 days
- Genital herpes, recurrent: 800 mg twice daily for 5 days
- Genital herpes, suppression: 400 mg twice daily
- Shingles: 800 mg five times daily for 7–10 days
- Headache
- Nausea
- Abdominal pain
- Dizziness
- Acute kidney injury (especially with dehydration or high doses)
- Central nervous system effects such as confusion or hallucinations, mainly in older or renally impaired patients
- Thrombotic thrombocytopenic purpura / hemolytic uremic syndrome in advanced HIV or transplant patients at high doses
- Nausea
- Vomiting
- Diarrhea
- Headache
- Malaise
- Acute kidney injury (especially with dehydration or rapid IV dosing)
- Neurologic effects such as confusion, tremor, or hallucinations, mainly with renal impairment
- Thrombotic thrombocytopenic purpura / hemolytic uremic syndrome in severely immunocompromised patients
- Adults with genital herpes, cold sores, or shingles
- People who prefer fewer daily doses than acyclovir
- Adults and children with genital herpes, cold sores, shingles, or chickenpox
- People for whom the lowest medication cost is a priority
- Known hypersensitivity to valacyclovir or acyclovir
- Known hypersensitivity to acyclovir or valacyclovir
- Reduce the dose in kidney impairment
- Maintain adequate hydration
- TTP/HUS has occurred at high doses in severely immunocompromised patients
- Use caution in older adults, who are more prone to CNS side effects
- Reduce the dose in kidney impairment
- Maintain adequate hydration
- Requires more frequent daily dosing than valacyclovir or famciclovir
- Use caution in older adults, who are more prone to CNS side effects
Bottom line: which should I choose?
Choose valacyclovir for simpler dosing, once or twice a day instead of up to five times, which makes a course easier to finish correctly. Choose acyclovir when the lowest price matters most, since it is very inexpensive and equally effective if taken on schedule. Both work best when started early, both are adjusted for kidney function, and either can be prescribed after a clinician reviews your history.
Common questions
Care for real conditions, prescribed online
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