Acyclovir Vs Valacyclovir

Acyclovir and Valacyclovir are prescription medications that are widely used to treat herpes infections including genital herpes and cold sores. Both medications work similarly. These drugs work by stopping the herpes virus from reproducing and spreading however they possess some differences. 

In this blog, we will discuss how these two treatments, Acyclovir and Valacyclovir differ from each other and which one is better for herpes infections.

What is Herpes?

Before knowing the medication first let’s have a quick review of the herpes virus. The Herpes virus belongs to a family of viruses called HSV or Herpes simplex Viruses. Generally, these viruses infect the skin causing blisters and sores.

When the herpes virus causes infection on your face, it is called cold sores and when it occurs around the genital area it is called genital herpes infection.  Unfortunately, herpes can not be cured but it can be managed effectively with medications such as Acyclovir and Valacyclovir.

Once the herpes virus infects you, it remains inside your body for life. Most of the time it stays inactive in the nerve cells of your skin and does not show any symptoms. The virus reactivates every once in a while and you get an outbreak of sores, blisters and other symptoms.

This viral infection can significantly influence the life of the sufferer as it causes cold sores, genital lesions and dangerous eye infections. Herpes simplex virus has two main types HSV-1 and HSV-2. HSV-1 is mainly responsible for oral cold sore lesions. Herpes simplex virus type 2 is mainly responsible for genital and rectal lesions.

Herpes simplex virus is contagious and it influences a huge portion of the population. As per WHO (World Health Organization), herpes simplex virus type 1 touches around two-third of the worldwide population and herpes simplex virus type 2 touches over 500 million people.

Acyclovir and Valacyclovir are antiviral medications that are prescribed to treat HSV infections and avoid spreading these infections to others. These medications can significantly impact the sufferer’s symptoms and life quality.

What Do You Need To Know About Oral Acyclovir?

Aciclovir 400 mg Tablets | Aciclovir Medication for Herpes Infections

Acyclovir is a generic name drug sold under brand names such as Sitavig and Zovirax. Usually, oral Acyclovir is prescribed to treat these infections. You need to swallow the pill with a glass of water. Acyclovir is also available in the form of a cream, which can be applied directly to the infected skin.

Acyclovir is a well-known antiviral drug used to treat herpes infections. It acts by averting the virus’s growth and spreading. When a person is exposed to herpes simplex or the virus reactivates it spreads through the skin cells. The virus uses the natural DNA replication process of cells to make its copies so that it can enter and infect other cells of the body.

Acyclovir stops this process by blocking an enzyme called DNA polymerase from working. This enzyme is required to copy the DNA of the herpes virus. Acyclovir mimics DNA polymerase enzyme taking its place but then working differently. It slows the virus spreading process and allows the immune system to clear this virus from skin cells.

What Do You Need To Know About Valacyclovir?

Valacyclovir Tablets | Valacyclovir Group Medication | Acyclovir Vs. Valacyclovir

Valacyclovir is also an antiviral medication similar to Acyclovir. Valacyclovir is a generic name drug sold under brand name versions such as Valtrex. It is among the most widely used medications to treat herpes. Valacyclovir has been approved for herpes treatment since 1995 and has a consistent safety record.

It is prescribed to manage herpes infections and reduce the severity of outbreaks and prevent outbreaks from happening. Usually, Valacyclovir is available as an oral pill that you need to swallow with a glass of water.

Valacyclovir works precisely the same as Acyclovir. It blocks the enzyme DNA polymerase from working, discontinuing the virus from replicating. When you take Valacyclovir, your body converts it into Acyclovir.

Are Acyclovir And Valacyclovir The Same Medications?

Chemically, Valacyclovir and Acyclovir are almost similar medications but these are not exactly the same. Acyclovir prodrug Valacyclovir work similarly to Acyclovir. During the first-class metabolism of the oral dosage form, Valacyclovir is transformed into acyclovir, letting more active ingredients be absorbed from the oral administration of the drug and also allowing more amount of time between the doses.

Acyclovir Vs. Valacyclovir


Acyclovir is a prescription-only drug available as tablets, oral suspension creams and injections. It was discovered in the 1970s and was broadly used as an effective treatment for herpes infections for decades.

Acyclovir encourages faster recovery during an oral or genital herpes outbreak and reduces the risk of transmitting the virus to other people. Acyclovir does not eliminate the herpes virus from the body of an infected person, it helps manage symptoms and improve the healing time.


Valacyclovir is a prodrug of Acyclovir which means it transforms into Acyclovir inside the body. It is a prescription medication only available in the form of oral tablets. Valacyclovir treats herpes simplex virus infections by stopping them from reproducing.

Valacyclovir is considered among the most effective herpes medications. Studies reveal that it reduces the amount of time needed for healing during a herpes outbreak and also reduces the risk of transmitting herpes virus to other people.

Valacyclovir starts working as soon you take it and it is extremely effective against all types of herpes virus. The dosage of Valacyclovir differs depending on what you need to treat shingles, genital herpes or outbreaks of oral herpes.

The Key Difference Between Acyclovir And Valacyclovir Antiviral Drugs

Acyclovir is a commonly used prescription medication to treat herpes simplex virus and varicella zoster virus. It belongs to the antiviral class of drugs known as synthetic purine deoxynucleoside analogues. This class of drugs is sometimes also referred to as nucleoside and nucleotide DNA polymerase inhibitor antivirals.

Acyclovir combats viral infections by integrating itself into the viral DNA and then barring viral DNA synthesis. It comes in multiple forms such as oral tablets, oral capsules, oral suspension, oral dissolving tablets, topical cream and ointment, ophthalmic ointment and solution for injection.

Acyclovir oral formulation has poor bioavailability as it is changed in first-pass metabolism, leading to poor absorption from the gastrointestinal tract.

Valacyclovir (Valtrex) is also an antiviral prescription medication commonly used for the treatment of herpes simplex virus and varicella zoster virus. It is the L-valyl ester of Acyclovir. To put it more simply, it is the prodrug of Acyclovir. First-pass metabolism eliminates most acyclovir from circulation and that is why the oral bioavailability is low for Acyclovir.

In contrast, first-pass metabolism transforms Valacyclovir to Acyclovir making it available to the body. The oral bioavailability of Acyclovir is 10-20% while Valacyclovir is as high as 54%. The process of first-pass metabolism also makes differences in how often these drugs must be dosed.

Acyclovir must be dosed 3-5 times a day depending on the indication while Valcyclovir is usually once or twice a day depending on the indication. Valacyclovir is only accessible as oral tablets with strengths of 500 mg and 1000 mg.

Although Valcayclovir is converted into Acyclovir, Valacyclovir seems to be a more effective medication. It is because Valcyclovir is absorbed better in the body than Acyclovir. So, even when you take Valacyclovir, it becomes Acyclovir in your body, you are likely to get more of it into your system if you swallow Valacyclovir than Acyclovir.

Research demonstrates that you can treat herpes infections similarly or better by taking Valcyclovir instead of Acyclovir. As Valacyclovir is better absorbed into your system you need to take Valacyclovir less often than Acyclovir and still get the same or better results. Typically Valcyclovir tablets are prescribed to take twice a day while acyclovir tablets are prescribed to take five times a day.

What Conditions Can Acyclovir And Valacyclovir Treat?

Both of these drugs are prescribed to treat genital herpes, cold sores, shingles and chickenpox. Acyclovir is also used to treat herpes simplex encephalitis, herpes of the brain and herpes in newborn babies. Acyclovir and Valacyclovir also play a critical role in the prophylaxis of these kinds of infections such as recurrent genital herpes.

Acyclovir and Valacyclovir both are used off-label to treat ocular infections linked to shingles and the prevention of cytomegalovirus. Off-label use of medication means a treatment that is not approved by FDA (US Food and Drug Administration).

Acyclovir is used to treat neonatal herpes simplex virus, neonatal herpes simplex virus prophylaxis, herpes simplex encephalitis, herpes labialis, herpes labialis prophylaxis, herpes genitalis, herpes genitalis prophylaxis, herpes zoster (shingles), varicella (chicken pox) and acute herpes simplex keratitis.

Off-label uses of acyclovir include against varicella zoster encephalitis, cytomegalovirus (CMV) prophylaxis, post-exposure varicella prophylaxis, herpes simplex ocular infection prophylaxis and herpes zoster ocular infection.

Valacyclovir treats herpes labialis, herpes labialis prophylaxis, herpes zoster (shingles), herpes genitalis, and varicella (chickenpox). Off-label uses of Valacyclovir include against herpes genitalis prophylaxis, cytomegalovirus (CMV) prophylaxis, post-exposure varicella prophylaxis and herpes zoster ocular infection.

Effectiveness Of Acyclovir And Valacyclovir

Acyclovir Tablets | Acyclovir Group Medications | Acyclovir Vs. Valacyclovir

Both of these medications work similarly and both are effective. In a study, participants who took Acyclovir and Valacyclovir showed the same results after taking these medications for a year. As mentioned above the key difference between these two drugs is that Valcyclovir has more bioavailability and a  longer duration of action than Acyclovir.

It means Valacyclovir needs to be taken a few times a day than Acyclovir and still it has the same or even better effect. For instance, Valacyclovir is usually taken two times a day while Acyclovir is usually taken up to five times a day depending on the condition and its severity.

A small study also demonstrated that people who took Valacyclovir were less likely to spread the herpes infection to other people than those who took Acyclovir.

Study 1

In an international level double-blind, randomized trial, Acyclovir and Valacyclovir were compared in the treatment of first episodes of genital herpes infections. Acyclovir was given 5 times daily and oral Valacyclovir was given twice a day. Clinically, no significant difference was noticed in the duration of pain, lesion healing or symptoms.

Valacyclovir offers the advantage of fewer doses. The decreased pill burden rises the likelihood that patients will take the schedule as prescribed until completion. Your doctor determines the best treatment for genital herpes however twice daily dosing may be an plus for Valacyclovir.

Study 2

In another double-blind, randomized clinical trial, Acyclovir and Valacyclovir oral tablet doses were compared for a herpes zoster infection known as shingles. The outcomes of this study demonstrated that Valacyclovir significantly enhanced the resolution of pain associated with a  shingles rash. While the rash rhealed itself, at the same time with either treatment regimen, there were fewer ocular complications in patients treated with Vlacyclovir.

Another considerable advantage of Valacyclovir found during this study was that it is only required to be dosed 3 times a day as compared to 5 times a day for Acyclovir. Ultimately your doctor or healthcare provider better knows which treatment option is best for you to treat active herpes zoster infection.


Acyclovir treatment is prescribed to neonates, infants, children, adolescents and adults. A standard dosage of Acyclovir is 400 mg tablets 3 times per day for 5 to 10 days and for the long term in case of prophylaxis treatment.

Valcyclovir oral doses are typically prescribed to children, adolescents and adults. A standard dosage of Valacyclovir is 1000 mg tablet twice a day for 2 to 10 days and in case of prophylaxis treatment for the long term.

Before Taking Acyclovir And Valacyclovir

Before taking Valacyclovir, tell your doctor or healthcare provider if:

  • You are allergic to Valacyclovir group medications, Acyclovir or any other drugs.
  • You are taking other medications particularly if you are taking vitamins, cimetidine (Tagamet) or probenecid (Benemid).
  • You have liver or kidney problems, HIV or AIDS or any other immune system problems.
  • You are pregnant, planning to get pregnant or breastfeeding your baby.

Similarly, before taking Acyclovir, make sure your doctor knows if:

  • You are allergic to Acyclovir group medications, Valacyclovir or any other medications.
  • You are pregnant, trying to be pregnant or breastfeeding.
  • You have liver diseases, kidney disease, HIV or AIDS or any disease that weakens the immune system.
  • You are taking any vitamins, herbal products, or nutritional supplements.
  • You are taking other medications that can interact with Acyclovir such as HIV medications (Retrovir), Sulphonamides (Bactrim), Probenecid (Benemid), Amphotericin B (Fungizone) and non-steroidal anti-inflammatory drugs (Ibuprofen).

Side Effects

Like any other medications, both of these drugs may cause some side effects. Some common side effects of Valacyclovir (Valtrex) include headache, vomiting, constipation, diarrhoea, abdominal pain, tiredness and joint pain. Rare side effects of this drug are fever, confusion, itching, rash, blood in the urine and yellowness of skin or eyes.

Common side effects of Acyclovir medication include vomiting, upset stomach, diarrhoea, dizziness, joint pain, tiredness, hair loss and vision changes. Serious side effects of Acyclovir are rare and may include itching, hives, rashes, rapid heartbeat, trouble breathing, weakness, trouble sleeping, fever, bloody diarrhoea, blood in urine, confusion, hallucinations, seizures, loss of consciousness and swelling of the throat, face, lips, tongue and limbs.

Drug Interactions

Certain medications, herbal supplements, vitamins or ingredients may cause drug interactions with Acyclovir and Valacyclovir. Drug interactions can influence how your medications work against the infection and may increase the risk of side effects or adverse events. So you need to keep some things in mind while taking acyclovir or Valacyclovir medication.

Acyclovir and Valacyclovir may have negative effects on the liver and kidneys which is why you should not take these medications with nephrotoxic or hepatotoxic drugs. the risk can be so severe that the simultaneous use of these medications is contraindicated. This is the case with Cidofovir.

Other drugs that should be strictly avoided to use with Acyclovir and Valcyclovir due to similar concerns include Mannitol, Foscarnet and capreomycin.

There are vaccinations available against varicella and zoster that significantly reduce the outbreaks of these viruses. However, the administration of these vaccinations depends on the immune system and the natural response of the body to produce antibodies in order to be effective. For that reason, Valacyclovir and Acyclovir medications should not be administered within a specific time before and after administering these vaccines.

It does not contain a comprehensive list of drug interactions. Make sure you discuss with your doctor or pharmacist about the potential drug interactions before starting with these medications.


The cost of Acyclovir and Valacyclovir depends on certain factors such as pharmacy, country, insurance coverage and whether you are buying a generic or brand-name drug.

Valacyclovir (Valtrex) 500 mg pack of 30 tablets usually cost around $421. Generic Valacyclovir costs less than brand-name drugs with or without insurance.

Generic Acyclovir costs around $19 without insurance. However, the drug is covered by most insurance and Medicare plans so you may get it at a cheaper cost.

Acyclovir And Valacyclovir During Pregnancy

There has been no drug-related risk of major birth defects in pregnant women. There is no sufficient data available about miscarriages due to the use of Acyclovir or Vlacylovir during pregnancy. However, there are known risks to untreated herpes simplex virus infections during pregnancy. Primary herpes infections during the first trimester of pregnancy may cause neonatal chorioretinitis, skin lesions and microcephaly. Your healthcare provider can give you the best treatment advice.

Is It Ok To Take Both Acyclovir And Valacyclovir At The Same Time?

No, it’s not ok to take Acyclovir and Valcyclovir medication at the same time. Valacyclovir is transformed into Acyclovir inside your body, so if you take both drugs at the same time, you are taking too much of Acyclovir.

It can result in an Acyclovir overdose and increase your risk of adverse effects including serious side effects such as kidney damage. Take one of these medications at a time and do not take any of these drugs without consulting a doctor. Also, make sure you take Acyclovir and Valcyclovir always as prescribed by your health care professional.

Acyclovir Or Valacyclovir: Which Is Better For Cold Sores?

Valacyclovir is considered the most effective treatment for cold sores. It effectively stops the herpes simplex virus from spreading in the body and increases the healing process of cold sores. Even though Acyclovir is also an effective treatment for cold sores, Valacyclovir has a longer duration of action and plasma availability so it can be taken just a few times a day.

However, the price point of Acyclovir often makes it the treatment of choice. People prefer Acyclovir considering that the effectiveness is equal at a cheaper price when taken as prescribed and at proper dosing intervals.

The top reason for using Valacyclovir over Acyclovir to treat cold sores is its higher level of oral bioavailability. When taken orally, Acyclovir is almost entirely broken down by the liver, whereas Valacyclovir has an oral bioavailability level of approximately 50% compared to 12% for oral Acyclovir.

Acyclovir Or Valacyclovir Which Is Better For Genital Herpes?

Acyclovir and Valcyclovir both drugs are both effective against all types of herpes virus with varying doses to treat outbreaks of genital herpes and oral herpes. Acyclovir is sometimes used to prevent genital herpes outbreaks in people who are exposed to the virus.

For adolescents and adults with a  first clinical episode of genital herpes infection, a standard dose of Aciclovir over Valacyclovir is prescribed. When taken daily for 4 months to 10 years, Acyclovir significantly reduced the frequency and severity of recurrent genital herpes in over 95% of people.

However, most doctors and healthcare professionals prefer Valacyclovir to acyclovir for the treatment of herpes due to the easier dosing regimen. Although Valacyclovir does not cure genital herpes, it effectively helps relieve pain and discomfort and allows sores to heal faster.

Acyclovir Or Valacyclovir, Which One Is Better For Shingles?

A double-blind, randomized, controlled clinical trial demonstrated that Vlacyclovir significantly reduces the pain symptoms related to shingle outbreaks quicker than SAcyclovir. Valacyclovir shingles treatment was also associated with fewer ocular complications due to shingles which can be destructive and tough to treat.

Concluding Words

Is Valacyclovir stronger than Acyclovir? Necessarily Vlacyclovir is not stronger than Acyclovir however Valayclovir is absorbed more efficiently in your body than Acyclovir. Every individual may respond differently to different types of drugs.

Both Acyclovir and Valacyclovir are safe and effective antiviral drugs however you may get superior outcomes with Valacyclovir than with Acyclovir. However, for the price point, Acyclovir is available at a cheaper cost compared to Valacyclovir.