Valacyclovir vs Acyclovir — Which Herpes Medication Is Better?

If you have herpes (HSV-1 or HSV-2) and your doctor mentioned medication, the two options you'll most likely hear about are valacyclovir (brand name Valtrex) and acyclovir (brand name Zovirax). Both are first-line antivirals. Both work. The choice between them comes down to dosing frequency, cost, and personal preference — not effectiveness.

Here's the honest comparison.

The bottom line

For most adults with genital herpes:

• Valacyclovir is more convenient (taken once or twice daily) and has better bioavailability — your body absorbs more of each dose.
• Acyclovir is cheaper as a generic ($4-15/month) but needs to be taken 3-5 times daily for outbreaks. Worse for adherence.
• Both have the same efficacy for outbreak treatment and suppression when dosed correctly.
• Side effect profiles are nearly identical — both are well-tolerated by most people.

If you're choosing between them and cost isn't a barrier, valacyclovir wins on convenience. If cost matters, generic acyclovir is fine.

How they actually work

Both drugs are nucleoside analogues that interfere with HSV replication. They get incorporated into the viral DNA during replication, which stops the chain. Critically:

• They only work in cells that are actively making more HSV (during reactivation/outbreak).
• They don't touch latent virus hiding in nerve cells.
• This is why neither is a cure — they just shorten outbreaks and reduce viral shedding.

Valacyclovir is a prodrug of acyclovir. Your body converts valacyclovir to acyclovir after absorption. The real difference: valacyclovir is absorbed about 3-5x more efficiently than oral acyclovir, so you need fewer/smaller doses.

Dosing comparison

For an active genital herpes outbreak (episodic treatment)

Valacyclovir:

• 1 g (1000 mg) twice daily for 7-10 days for the first outbreak
• 500 mg twice daily for 3 days for recurrent outbreaks
• OR single-dose 2 g twice in one day (also FDA-approved for recurrence)

Acyclovir:

• 400 mg three times daily for 7-10 days for the first outbreak
• 800 mg twice daily for 5 days, OR 400 mg three times daily for 5 days, for recurrence

For daily suppressive therapy (preventing outbreaks)

Valacyclovir:

• 500 mg once daily (if fewer than 10 outbreaks/year)
• 1 g once daily (if 10+ outbreaks/year)

Acyclovir:

• 400 mg twice daily

For cold sores (oral HSV-1)

Valacyclovir: 2 g twice in one day (single-day regimen)

Acyclovir: 400 mg 5 times daily for 5 days (rarely used since valacyclovir is much more convenient)

Cost comparison (US, 2026)

Generic acyclovir:

• $4-15/month at most pharmacies for daily suppressive dosing
• One of the cheapest prescription medications available

Generic valacyclovir:

• $10-25/month with GoodRx or insurance for daily suppressive dosing
• Brand-name Valtrex: $200-400/month without insurance (almost no one pays this — generic is widely available)

For uninsured patients on suppressive therapy, acyclovir saves $10-15/month vs valacyclovir. Across a year, that's about $120-180. Not huge but real.

When valacyclovir is the better choice

• You'll struggle with 3-5x/day dosing. Adherence is everything with antivirals; missing doses reduces effectiveness.
• You want the simplest single-day regimen for recurrent outbreaks. 2 g twice in one day vs. 5 days of acyclovir.
• You're on suppressive therapy long-term. Once-daily is much easier to maintain than twice-daily over years.
• You travel frequently or have irregular schedules. Fewer pills = easier to remember.

When acyclovir is the better choice

• Cost is a barrier and adherence to multi-times-daily dosing isn't an issue.
• You're already on it and tolerating it well. No reason to switch.
• You need IV antiviral therapy (for severe outbreaks, immunocompromise, or neonatal herpes — IV acyclovir is standard).
• Pregnancy — acyclovir has more accumulated safety data in pregnancy, though valacyclovir is also widely used and considered safe.

What about famciclovir?

Famciclovir (brand name Famvir) is a third option. It's a prodrug like valacyclovir but converts to penciclovir rather than acyclovir. Similar effectiveness, similar dosing convenience to valacyclovir, similar cost (generic ~$15-30/month).

Famciclovir is sometimes used for people who can't tolerate valacyclovir or in specific clinical scenarios. For most patients, it's a third-line choice not because it's worse but because acyclovir and valacyclovir have more accumulated experience.

Side effects — they're really mild

Both medications have very mild side effect profiles. Most common (in less than 10% of patients):

• Headache
• Nausea
• Mild abdominal pain
• Dizziness

Rare side effects:

• Kidney issues (especially with dehydration or IV high-dose)
• Hallucinations or confusion (rare, mostly in elderly or kidney-impaired)
• Allergic reaction (rare)

Both medications have been used in millions of patients across decades. The safety profile is well-established.

Resistance

True acyclovir/valacyclovir resistance is rare in immunocompetent patients (under 1%). When it happens, it's almost always in immunocompromised patients — HIV with low CD4, transplant recipients, advanced cancer patients on chemo.

For resistant cases:

• Foscarnet (IV) is the standard alternative
• Cidofovir (IV or topical) is another option
• Pritelivir (helicase-primase inhibitor, currently in late-stage trials) — active against acyclovir-resistant HSV

Suppressive therapy — how effective is it?

For someone with 6+ outbreaks/year, daily suppressive therapy:

• Reduces outbreak frequency by 70-80%
• Reduces transmission risk to sexual partners by about 50%
• Reduces asymptomatic viral shedding significantly

It's the single most evidence-backed way to manage frequent recurrences. Talk to your doctor if outbreak frequency is interfering with your life.

How to switch between them

If you're on one and want to switch to the other:

• No washout period needed
• Just start the new one at its standard dose
• Tell your doctor so they can update the prescription

Bottom line table

Both work. The choice is yours to make with your doctor based on what fits your life.

For more on herpes — outbreak triggers, transmission, cure trials, life after diagnosis — see our complete herpes pillar guide.