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HomeHealth ConditionsShingles

Valacyclovir vs. Acyclovir: Which Is Better for Shingles?

Brian Leonard, PharmD, BCACP, BCGPChristina Aungst, PharmD
Published on June 29, 2022

Key takeaways:

  • Valacyclovir (Valtrex) and acyclovir (Zovirax) are antiviral medications used to treat shingles. They can help your skin heal and reduce the pain caused by shingles. 

  • Valacyclovir and acyclovir are taken by mouth multiple times a day. But acyclovir needs to be taken more frequently since it’s not absorbed as well as valacyclovir.

  • In general, one medication isn’t recommended over the other. But valacyclovir requires fewer pills. Your healthcare provider will determine which is best for you.

A person holding two medications and looking them up online.
Tashi-Delek/E+ via Getty Images

If you’re age 50 or older, you’ve probably started hearing more about shingles (herpes zoster), a painful skin rash from the virus that causes chickenpox. That’s because you’re more likely to develop shingles at this age.

The good news is there’s a vaccine that can lower your risk of developing shingles. And you’re eligible to get it once you turn 50. But if you’re one of the roughly 33% of adults who end up with shingles, there are a few medications available to treat it. 

Valacyclovir (Valtrex) and acyclovir (Zovirax) are two treatment options for shingles. These medications may sound similar, but they’re not the same. 

So, how exactly are they different? And is one better than the other? Below we’ll discuss what you should know about valacyclovir versus acyclovir for treating shingles. 

What is valacyclovir?

Valacyclovir is a prescription medication that’s FDA-approved to treat a few conditions caused by viruses. This includes shingles, genital herpes, and cold sores in adults. In children, it’s approved to treat chickenpox and cold sores.

Valacyclovir is available as an oral tablet in two strengths: 500 mg and 1,000 mg (1 g). You can find it both as brand-name and generic products.

What is acyclovir?

Acyclovir is also a prescription antiviral medication. The oral tablet, capsule, and liquid forms are FDA-approved to treat shingles, genital herpes, and chickenpox in adults. They can also treat chickenpox in children.

When treating shingles, you can find acyclovir in the following dosage forms and strengths, which are available as generic products:

  • Tablets: 400 mg and 800 mg

  • Capsules: 200 mg

  • Oral suspension: 200 mg/5 mL

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How do valacyclovir and acyclovir work for shingles?

Valacyclovir is a prodrug of acyclovir. That means it’s converted into acyclovir (the active component) in the liver after being absorbed in your gastrointestinal tract (the stomach and intestines). Valacyclovir is formulated this way to help more acyclovir reach your bloodstream. That’s because acyclovir is poorly absorbed when taken on its own.

Both medications work against varicella zoster — the virus that causes shingles (and chickenpox). They do this by interfering with the virus’s DNA. DNA is necessary for the virus to make copies of itself. 

Keep in mind: Valacyclovir and acyclovir won’t cure shingles. But by stopping the virus from copying itself, they can prevent it from spreading throughout your body.

How are valacyclovir and acyclovir dosed and given?

The usual valacyclovir dose for shingles is 1 g by mouth 3 times a day for 7 days. 

Acyclovir isn’t absorbed as well as valacyclovir, so it has to be taken more frequently. The usual acyclovir dose for shingles is 800 mg by mouth 5 times a day for 7 to 10 days. Severe infections may require intravenous (IV) treatment

You can take valacyclovir and acyclovir with or without food. If they upset your stomach, try taking them with meals or a snack. For both medications, your recommended dosage may be lower if you have kidney problems.

How effective are valacyclovir and acyclovir for shingles?

Valacyclovir and acyclovir are both effective shingles treatments if you start taking them within 72 hours of getting the shingles rash. They can help make your skin rash and pain go away more quickly.

Acyclovir has been shown to speed up the healing of skin blisters and rashes by a couple days

And one study showed that shingles pain went away within an average of 41 days (about 1 and half months) in older adults taking acyclovir. This is compared to an average of 101 days (more than 3 months) for people taking placebo (a pill without medication in it).

Another study of over 1,000 adults compared 7-day courses of valacyclovir and acyclovir for shingles. Pain resolved significantly faster with valacyclovir (38 days) compared to acyclovir (51 days). There were no significant differences in skin healing between the two medications. 

In general, one medication isn’t recommended over the other. But if you want to take fewer pills, valacyclovir offers less-frequent dosing. Your healthcare provider will determine which option is best for you.

What are the known side effects of valacyclovir and acyclovir?

The side effects of valacyclovir and acyclovir are very similar. They’re also usually mild and resolve on their own. See the most common side effects from a head-to-head study compared below:

Side effect

Valacyclovir (7-day course)

Acyclovir (7-day course)

Nausea

16%

19%

Headache

11%

13%

Vomiting

9%

8%

Diarrhea

7%

7%

Constipation

5%

5%

Dizziness

4%

6%

Weakness

4%

5%

What are the serious side effects of valacyclovir and acyclovir?

Although rare, serious side effects are possible with valacyclovir and acyclovir. This includes hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). HUS is when you develop blood clots along with low levels of platelets (cells that help your blood clot) and kidney damage. TTP is similar, but also includes fever and neurological (brain and nervous system) effects.

TTS and HUS have occurred at doses higher than what’s usually taken for shingles. People with weakened immune systems (like advanced HIV) and certain transplant recipients may be at higher risk.

Other serious side effects include acute kidney injury and neurological problems (like agitation, confusion, hallucinations). These effects may be more likely to happen if you’re older, have kidney problems, or are taking higher-than-recommended doses.

What interactions do valacyclovir and acyclovir have?

Valacyclovir and acyclovir don’t have any known significant interactions with other medications. 

However, it’s still important to give your healthcare provider and pharmacist your current medication list to check for potential issues. For example, other medications that cause kidney damage may raise the risk of kidney problems from valacyclovir or acyclovir.

How much do valacyclovir and acyclovir cost?

Valacyclovir and acyclovir are both available as lower-cost generic medications. The average retail price of acyclovir tends to be less expensive than the average retail price of valacyclovir

But by using a free GoodRx discount, you can find 7-day courses of either medication for less than $10 at certain pharmacies. 

The bottom line

Valacyclovir and acyclovir are effective medications for treating shingles. They work best if started within 72 hours of getting the shingles rash. Both medications have similar side effects and cost about the same with a GoodRx discount.

The biggest difference is that you have to take acyclovir more often than valacyclovir. Your healthcare provider will take into account your preferences and other factors to determine which is best for you.

References

A-S Medication Solutions. (2021). Acyclovir tablets [package insert].

American Academy of Dermatology Association. (n.d.). Shingles: Who gets and causes.

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Beutner, K. R., et al. (1995). Valaciclovir compared with acyclovir for improved therapy for herpes zoster in immunocompetent adults. Antimicrobial Agents and Chemotherapy.

Bhandari, J., et al. (2022). Hemolytic uremic syndrome. StatPearls

Centers for Disease Control and Prevention. (2019). Treating shingles (herpes zoster).

DailyMed. (2020). Acyclovir suspension.

DailyMed. (2021). Acyclovir capsule.

DailyMed. (2021). Acyclovir injection.

GlaxoKlineSmith. (2021). Valtrex (valacyclovir) [package insert].

Gnann Jr., J. W., et al. (2007). Antiviral therapy of varicella-zoster virus infections. Human Herpesviruses: Biology, Therapy, and Immunoprophylaxis.

Karaman, R., et al. (2012). Prodrugs of acyclovir – A computational approach. Chemical Biology & Drug Design.

Nair, P. A., et al. (2021). Herpes zoster. StatPearls

Saguil, A., et al. (2017). Herpes zoster and postherpetic neuralgia: Prevention and management. American Family Physician.

Stanley, M., et al. (2022). Thrombotic thrombocytopenic purpura. StatPearls

Taylor, M., et al. (2021). Acyclovir. StatPearls

Trachtman, H. (2013). HUS and TTP. Pediatric Clinics of North America.

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

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