Acyclovir vs Famciclovir
Acyclovir (Zovirax) and famciclovir (Famvir) are both effective antivirals, but they differ in convenience. Acyclovir is the cheapest option, while famciclovir offers shorter, less frequent courses.
Antiviral (nucleoside analogue)
Antiviral (nucleoside analogue prodrug)
The original herpes antiviral — highly effective and inexpensive, but usually taken multiple times a day because of lower absorption.
A prodrug of penciclovir with convenient short-course dosing, often used for recurrent herpes, cold sores, and shingles.
Herpes / cold sores / shingles
Herpes / cold sores / shingles
- Genital herpes (treatment and suppression)
- Cold sores (herpes labialis)
- Shingles (herpes zoster)
- Chickenpox (varicella)
- Genital herpes (recurrent treatment and suppression)
- Cold sores (herpes labialis)
- Shingles (herpes zoster)
- 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
- Genital herpes, recurrent: 1 g twice daily for one day
- Genital herpes, suppression: 250 mg twice daily
- Cold sores: 1.5 g as a single dose
- Shingles: 500 mg three times daily for 7 days
- 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
- Headache
- Nausea
- Diarrhea
- Fatigue
- Acute kidney injury (rare, mainly with dehydration or renal impairment)
- Confusion, mainly in older or renally impaired patients
- Urticaria and other hypersensitivity reactions
- Adults and children with genital herpes, cold sores, shingles, or chickenpox
- People for whom the lowest medication cost is a priority
- Adults with recurrent genital herpes, cold sores, or shingles
- People who prefer very short treatment courses
- Known hypersensitivity to acyclovir or valacyclovir
- Known hypersensitivity to famciclovir, penciclovir, or the topical product Denavir
- 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
- Reduce the dose in kidney impairment
- Efficacy for a first (initial) genital herpes episode has not been established
- Maintain adequate hydration
- Use caution in older adults, who are more prone to CNS side effects
Bottom line: which should I choose?
Choose acyclovir when cost is the priority and frequent daily dosing is manageable. Choose famciclovir for simpler short-course regimens, such as a one-day treatment for recurrent herpes, if the higher price is acceptable. Both are equally effective when taken correctly, and both are adjusted for kidney function.
Common questions
Care for real conditions, prescribed online
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