Antivirals are used to treat herpes. Valacyclovir (Valtrex), acyclovir (Zovirax), and famciclovir (Famvir) are the most common of them.
Despite their assumed similarity, valacyclovir and acyclovir have several differences. Read further to learn more about valacyclovir and acyclovir, including their differences, similarities, and effectiveness.
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Valacyclovir is an FDA-approved prescription medication that treats medical conditions caused by the herpes virus. Valacyclovir works by inhibiting viral DNA replication.
The drug is available as an oral tablet in two strengths — 500mg and 1,000mg.
Valacyclovir is available as a generic and brand product. It is one of the most popular and effective antivirals for shingles, genital herpes, and cold sores in adults. Valacyclovir is approved to treat chickenpox and cold sores in children.
Acyclovir is an FDA-approved prescription medication that also treats conditions caused by the herpes virus. It comes in different forms and strengths to be used according to the prescribing doctor’s instructions.
These forms and their corresponding strengths include:
Acyclovir is also available as an injection or cream. It can treat shingles and genital herpes in adults and can treat chickenpox, including those in children.
Acyclovir and valacyclovir work similarly. However, valacyclovir has more bioavailability and a longer half-life than acyclovir. As such, one can take valacyclovir fewer times daily than acyclovir and still have similar effects.
Valacyclovir is typically taken twice daily, whereas acyclovir can be taken up to five times daily, depending on what it’s treating.
Small comparative studies failed to elucidate any increased efficacy of one over the other.¹
However, valacyclovir is preferred in clinical practice as it can be dosed less frequently, and acyclovir is dependent upon renal clearance.
In older adults, however, it may be problematic in the context of chronic kidney disease (CKD). However, acyclovir can be utilized intravenously in more severe infections where others can’t.
Shingles is a viral infection causing painful rashes on any body part. It typically resembles a single stripe (dermatome) of blisters wrapping around your torso’s left or right side.
This condition is caused by the varicella-zoster virus — the same virus that causes chickenpox. So once you have had chickenpox, the virus will remain in your body and reactivate later as shingles.
Despite being possibly painful, shingles isn’t typically life-threatening. You can get vaccinated to reduce the risk of developing shingles. Getting early treatment can shorten shingles infections and reduce the chances of complications like postherpetic neuralgia.
Shingles symptoms typically affect only a tiny section on one side of your body. The symptoms include:
Pain, burning, or tingling sensation
Fluid-filled blisters that break open and crust over
A red rash that begins a few days after the pain
Sensitivity to touch
Pain is often the first, the most prevalent symptom of shingles and can be intense in some people.
Contact your doctor immediately if you suspect you have shingles, especially under these conditions:
The rash is painful and widespread
You are 50 years or older (age increases complication risks)
The rash and pain occur near the eye, which can lead to long-term eye damage if left untreated
Either you or a family member has a weakened immune system due to medications, cancer, or chronic illness
There is no cure for shingles. However, early treatment using antiviral drugs can speed up healing and reduce your risk of compensation.
Common antiviral drugs used to treat herpes (shingles) include:
Doctors may also prescribe:
Anti-inflammatory drugs like ibuprofen to reduce pain and swelling
Narcotic medication or painkillers to reduce pain
Antihistamines such as diphenhydramine to reduce itching
Valacyclovir and acyclovir are effective against all forms of the herpes virus, with varying doses used to treat outbreaks of genital herpes, shingles, and oral herpes. However, most doctors prefer valacyclovir to acyclovir for treating herpes due to easier dosing.
The table below depicts the difference between Valacyclovir and Acyclovir.
The main similarity is that both valacyclovir and acyclovir have the same mechanism of action, and valacyclovir is converted to acyclovir in the body.
Valacyclovir is a generic drug and is also available as a brand-name drug known as Valtrex. On the other hand, acyclovir is available under different brand names, such as Zovirax, SITAVIG, and Avaclyr.
Valacyclovir works best if taken 72 hours after the first symptom of shingles or genital herpes appears. It also works best if used 72 hours after symptoms start to appear for recurrent outbreaks of genital herpes. However, the earlier the treatment, the better.
Best practices when taking valacyclovir for shingles include:
Take the drug for the full treatment period even if the symptoms start to disappear
Depending on the prescribing doctor and the individual, Valacyclovir dosage will vary. Follow the doctor’s prescription or instructions on the label. Generally, the recommended dosage for treating shingles in adults is 1000mg three times daily for seven days. For kids, ensure you follow the doctor’s prescription accurately.
Acyclovir usage is advised as soon as you notice the first symptom of shingles or herpes infection. Acyclovir oral suspensions, tablets, or capsules can be taken on an empty stomach or with meals. The bioavailability of acyclovir is not affected by food.
Best practices when using Acyclovir include:
Take it for the full treatment duration
Acyclovir dosage differs across individuals and doctors. The amount you take will depend on the strength of the medicine. The recommended acyclovir dosage is 200mg every four hours or 400mg every 12 hours.
Although both drugs are effective in treating shingles and herpes, they are not without side effects. These include the following:
Each drug has a separate list of possible side effects. The side effects of valacyclovir include:
Increased liver enzymes
Reduced white blood cells
On the other hand, the side effects of acyclovir include:
Usage of these drugs isn’t advisable for individuals with hypersensitivity to either medicine. Ask your doctor to ensure whether you’re fit to use either of these drugs.
In fact, in June 2022, Health Canada found a link between valacyclovir and DRESS syndrome after a safety review, which was initially elucidated by the European Medicines Agency.²
Both drugs can negatively impact the kidney and liver. Therefore, using valacyclovir and acyclovir with nephrotoxic and hepatotoxic drugs can be hazardous. These drugs include mycophenolate, tenofovir, foscarnet, and theophylline.
As much as vaccines can help prevent shingles, the production of antibodies by the immune system depends on how one reacts to live attenuated vaccines. As such, valacyclovir and acyclovir must not be administered before or after the varicella virus vaccine, as they can diminish its effectiveness.
Make sure to inform your healthcare provider of any prescription drugs and supplements you’re taking before taking valacyclovir or acyclovir.
Valacyclovir and acyclovir are effective solutions to treat shingles or herpes. However, proper dosage is necessary to avoid the side effects.
In addition, early treatment of shingles and herpes is advisable to keep the condition from worsening and threatening your life. One of the first signs is rashes and pain. You should consult your doctor immediately if you notice these or any other symptoms of shingles and consider antiviral medications like valacyclovir and acyclovir.
No, it doesn't. Valacyclovir treats herpes viruses but not influenza or SARS-CoV-2.
No, valacyclovir and acyclovir are different antiviral medications. However, valacyclovir is metabolized to acyclovir in the body, and both target the same viruses.
Valacyclovir doesn’t cure herpes or shingles. However, it is effective in relieving pain and discomfort as well as speeding up recovery.
Although acyclovir won’t cure all herpes, it can help reduce pain and discomfort and heal sores faster.
According to the CDC, suppressive therapy can reduce the frequency of herpes recurrence by 70% to 80%.³
It can take up to 10 — or even longer for some people — for herpes to heal with valacyclovir treatment.
Valacyclovir can take effect swiftly and provide some relief in as little as 2–3 days. The earlier you start taking valacyclovir, the faster and more effective it will be.
No, it isn't. Valacyclovir and acyclovir target the same viruses.
No, valacyclovir and acyclovir are all safe. They are both FDA-approved drugs and are used to effectively treat shingles, HSV-1, HSV-2, and other forms of herpes.
Both antiviral drugs work by interfering with viral DNA replication.
These antivirals are used to treat or prevent infections caused by the herpes zoster, herpes simplex, and varicella-zoster viruses.
Yes, valacyclovir and acyclovir are considered safe for use during pregnancy. Although no controlled studies have been performed, large observational studies have provided reassuring data. However, if you use ointment or cream on the skin surrounding the breasts, wash the area with water and gentle soap before allowing the baby to breastfeed.
Avoid sexual intercourse to keep you from spreading the herpes virus. Also, avoid touching infected areas and then touching your eyes.
Summary safety review - - Health Canada | Government of Canada
Genital herpes | Centers for Disease Control and Prevention
Valacyclovir vs acyclovir: 9 things that make them different | Strut Health
Acyclovir | Drugs.com
Valtrex (Valacyclovir) | Everyday Health