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Zovirax vs. Valtrex vs. Famvir What You Need to Know

<p>Zovirax vs. Valtrex vs. Famvir What You Need to Know</p>
Fernando Mariz Picture of Fernando Mariz

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Written by our editorial team.

Last Edited 5 min read

The immune system is an automated defense mechanism that stops infectious microorganisms, like bacteria, viruses, and fungi, from invading our bodies. It does this through a complex network of cells and organs, but even a network as strong as this can be penetrated, sometimes causing us to become sick. In these cases, we arm ourselves with medication. 

Modern-day science has equipped us with thousands of treatments to sort out everything from the common sniffles to serious illnesses. Antiviral drugs are one class of medication created for treating viral infections. Unlike antibiotics, antiviral drugs do not destroy their target. Instead, they hinder their development. Quite a clever approach considering viral infections can be difficult to manage. 

Below we take a better look at 3 of the most common antiviral drugs on the market used to treat the herpes virus:

Basic Overview 


A long-standing creation by GlaxoSmithKline, Zovirax is an antiviral drug designed to treat infections caused by certain viruses. First released in 1985, the drug has been a reliable treatment for viruses such as Herpes Simplex Virus (HSV) type 1 and 2. 

The drug is available in oral and topical form and is used for short to medium-term treatment plans. When taken orally, the active ingredient, acyclovir, stops viruses from replicating themselves and spreading by targeting their underlying symptoms. The drug's potency stunts the growth of these viruses and prevents recurrence and outbreaks. 

In most cases, it is used to stop the recurrence of Genital Herpes. Although it doesn't eradicate the herpes virus completely, it drastically minimizes the pain and discomfort associated with symptom development. It helps sores heal much faster, reducing the active duration of the virus and patient downtime. 


Promoted by GlaxoSmithKline under the brand name Valtrex, Valacyclovir has been on the market since 1995. The product was created as an antiviral solution to viruses and is referred to as a prodrug, meaning it converts into another drug once it is metabolized by the body. Once consumed, the inactive substance valacyclovir is transformed into the active substance acyclovir. 

Acyclovir is the driving force behind the drug's effects. Valtrex is commonly used to manage the symptoms of HSV types 1 and 2, Epstein-Barr, and Varicella-Zoster. The active ingredient in the drug slows the virus's growth, multiplication, and spread to help the body fight the infection and associated symptoms. 

The symptom management approach aims to minimize the frequency and intensity of symptoms like cold sores, genital Herpes, shingles, and chickenpox that originate from the mentioned viruses. Valtrex can also be prescribed to prevent viral infections from occurring altogether. This is particularly the case in those who have undergone organ transplants and are at risk of infection from viruses such as cytomegalovirus.


A product by Novartis, Famvir is an antiviral treatment that has been on the market since 1994. The product uses the active ingredient penciclovir to execute its function and is considered a first-line treatment for viruses such as Herpes Zoster. 

The product stops viruses from making copies of itself, which impedes their infection rate. This prevents symptoms such as shingles and cold sores from growing in severity. The drug also helps with other viruses within the Herpes family, like Genital Herpes, and prevents the reoccurrence of the virus. 

Although the drug is an effective solution to Herpes, it does not cure the virus or stop its contagious nature. However, it may decrease symptoms of burning, pain, tingling, tenderness, and itching linked to the virus and accelerate the healing process of sores while preventing the possibility of new ones forming. 

How Do these Drugs Work?

When we face the wrath of a virus wreaking havoc on our body, it's only natural to wonder how the prescribed treatment works to fight infection and return us back to normalcy. The antiviral class of drugs is the most effective aid we have against viruses, and Zovirax, Valtrex, and Famvir belong to this class. These drugs were designed to stop the multiplication of viruses in the body, in simple terms, stop them from multiplying and making more copies of themselves to overthrow our immune system. 

This approach may seem ineffective as it leaves the virus dormant in the body. However, it is the only way to subside symptoms and stop the virus from spreading and invading healthy cells in the body. So, in essence, these drugs are a management tool, not a cure. However, consistent use of antiviral drugs can make living with an incurable condition like herpes much easier. 

Zovirax, Valtrex, and Famvir are taken during active phases of HSV-1 or HSV-2 infections to control and treat symptoms. They are also used as suppressive therapy for herpes to reduce the severity and frequency of outbreaks. This approach/mechanism of action is so effective that it can even help those with asymptomatic herpes lower their risk of spreading the virus to other people via oral or penetrative intercourse, which helps infected individuals live a normal life. 

Uses of Zovirax, Valtrex, and Famvir

Use lists or indication lists are the primary uses of medication. They tell us the purpose behind a treatment or, more simply, what it can be used for. Zovirax and Valtrex are FDA-approved to treat HSV types 1 and 2. In contrast, Famvir is approved to treat Herpes Zoster, also known as shingles. These drugs also have off-label uses, which means they can treat/manage other viruses for which they are unapproved. 

Below we look at off-label uses that are exclusive to each drug:

  • Zovirax Off-Label Uses 

-Shingles: A viral infection that results in a painful rash. It can appear on any part of the body and often resembles stripes. An NCBI study concludes Zovirax reduces residual pain linked to shingles development.

-Cold sores: Tiny fluid-filled blisters around the mouth or other areas of the face. 

-Chickenpox:  An itchy rash paired with fluid-filled blisters. In a placebo-controlled trial, Zovirax reduced new lesion formation, reduced the maximum number of lesions, accelerated cutaneous healing, and shortened fever durations.

  • Valtrex Off-Label Uses 

-Cytomegalovirus (CMV): A viral infection that can be transmitted from a pregnant mother to baby. It can cause brain and/or liver damage to the baby. A JAMA Network study states the drug suppresses the reactivation of CMV in those with critical illnesses.

-Bell's palsy: This is a temporary paralysis of one side of the face caused by the presence of a viral infection. A study shows that early therapy with Valtrex and prednisolone resulted in a better prognosis than using prednisolone alone. 

  • Famvir Off-Label Uses

-Chronic hepatitis B virus (HBV) infection: This is a severe liver infection caused by the hepatitis virus. According to a PubMed study, the long-term use of Famvir may reduce the level of HBV in the bloodstream (called the viral load). This helps slow down the progression of the disease.

-Initial outbreaks of Genital Herpes: Painful blisters (fluid-filled bumps) around genitals and anus that can open up and ooze fluid. The CDC (Centers for Disease Control and Prevention) recommends Famvir as one of the top antiviral 3 options for treating an initial herpes outbreak. 

- HSV-1 and HSV-2 symptoms: The drug can be used to manage symptoms of these conditions in patients with compromised immune systems.

Zovirax, Valtrex, and Famvir are effective and safe for both approved and unapproved uses due to their balanced potency and safety profiles. 

Efficacy and Safety 

The efficacy and safety of treatments are gauged by their ability to treat indicated conditions without causing distress to users. Several trials and research studies are dedicated to the antiviral drugs Zovirax, Valtrex, and Famvir. Their long-standing availability on the market has left these drugs open for testing by professionals and patients alike, which ultimately worked in their favor considering the number of successful outcomes noted from trials and positive reviews recorded. 

Below we look at evidence that demonstrates the favorable efficacy and safety profiles of these drugs:

  • Zovirax

A study sourced from the National Library of Medicine evaluated the efficacy and safety of oral acyclovir for Herpes and confirm the drug to be safe and effective. Many users noted significant changes in their symptoms with minimal side effects and experienced. They also added that acyclovir use provided the advantages of comparable healing times and convenient dosage schedules.

  • Valtrex

PubMed study evaluating the efficacy and safety of valacyclovir for Herpes found that the safety profile was similar to that of acyclovir. Valacyclovir was tolerated, safe, and effective for both the treatment and suppression of recurrent Herpes.

  • Famvir

Sciencedirect review evaluating the clinical efficacy and safety of famciclovir indicates that famciclovir is an effective option for treating and suppressing Herpes. Patients saw an improvement in their symptoms and experienced little to no side effects.

Dosage and Strength Explained

Although Zovirax, Valtrex, and Famvir are all antiviral drugs, they belong to different subclasses of drugs and use different active ingredients to execute their function. This means that their dosage and strength availability differs. The frequency of doses also varies depending on the virus being treated.

Here we look at some basic dosage and strength information of Zovirax, Valtrex, and Famvir:

Name of Drug

Medication class

Active compound

Lowest strength available 

Highest strength available


Synthetic nucleoside analog





Purine (guanine) nucleoside analog 

valacyclovir— acyclovir








It's important to note that these drugs work best when taken at the onset of symptoms or outbreak. Depending on the severity of symptoms, professionals will prescribe either a long-term or short-term treatment plan. Treatment plans should never be discontinued prematurely. Full courses must be completed on schedule for maximum results. Adherence to the prescribed dosage and frequency schedules is also important, as ignorance of them can cause undesirable outcomes. Patients are encouraged to increase their water intake to reduce kidney issues when taking these drugs.

Possible Side effects 

Zovirax, Valtrex, and Famvir have a great safety and tolerability profile with a low possibility of side effects if the drugs are used correctly. However, there are instances where common side effects might occur while the body is becoming familiar with the drug's effects. 

Common side effects include:

  • Headache

  • Fatigue 

  • Diarrhea, nausea, or vomiting

  • Abdominal pain or flatulence

  • Itching or paresthesia (pins-and-needles sensations or burning)

These side effects are typically mild and short-lived. Most users employ home remedies to get rid of them if they get troublesome. 

Interactions and Contraindications  

Contraindications and interactions are two instances that hinder the use of a particular treatment. Drug interactions occur when two or more incompatible treatments are used together. On the other hand, contraindications are health conditions or situations that don't allow specific treatment use. Interactions and contraindications can fuel serious side effects and risks.

Below we list common interactions and contraindications of Zovirax, Valtrex, and Famvir:


  • There are no clinically significant drug interactions linked to Zovirax, Valtrex, or Famvir use. However, experts do suggest that users avoid combining the use of these drugs or those very similar (same active components). 

  • Famvir can reduce the effect of a herpes zoster vaccine and varicella virus vaccine. Famvir can only be used 14 days after these vaccines have been administered.


  • Alcohol abuse

  • Severe anemia

  • Drug addiction

  • Severe depression

  • Recent organ transplantation

  • Uncompensated hypothyroidism

  • Rheumatoid arthritis or psoriasis

  • Severe liver or kidney issues/failure 

  • Significant neuropsychiatric syndromes

  • Active autoimmune diseases such as lupus erythematosus

The Bottom Line

Antiviral drugs such as Zovirax, Valtrex, and Famvir are one of the top-rated treatments for viruses such as Herpes. They can successfully manage outbreaks and associated symptoms without putting the body under stress. The effects produced by each drug are almost identical, with only a few differences seen in dosage, strength, and durational effects. Because the effects and approach of these drugs are so similar, no option is rated better than the other. 

Below we look at some quick facts about each drug:

  • Zovirax is the oldest antiviral medication available on the market since 1982 in topical form (ointment cream) and since 1985 as an oral pill. Being the oldest pill on the market, its reliability rate is quite high. There is also a lot of clinical evidence supporting its efficacy and safety in long and short-term use. This drug requires frequent standard administration.

  • Valtrex was approved by the FDA in 1995 and was the second antiviral medication available on the US market. It comes in an oral pill form and is a prodrug of acyclovir (the body converts an inactive compound into acyclovir after absorption). Valtrex has an improved bioavailability, allowing the body to absorb higher amounts of the drug—lower doses provide maximum effects. Due to this, frequent administration is not necessary, which caters to convenience. 

  • The active ingredient in Famvir was approved for use in 1994, giving it a reliable stance on the market as well. The drug has an excellent absorption rate and is typically prescribed for indicated use in cases where results are needed, but frequent administration is impossible. Once absorbed by the body, Famvir is transformed into a long-acting drug, requiring less frequent administration but still providing long-lasting, effective results. The product is often used as an alternative to Valtrex and Zovirax when treating patients with compromised immune systems.

The bottom line, Zovirax, Valtrex, and Famvir are all excellent antiviral drug choices. All 3 drugs have a great safety and efficacy profile and can successfully manage symptoms of viruses they are indicated to treat. Not to mention they have a long list of off-label uses, which can benefit patients who have reached their thresholds with other treatment options. The ideal treatment choice here will depend on various patient factors and the type/severity of the virus being treated.


8 Sources

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This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your physician about the risks and benefits of any treatment. Nu Image Medical may not offer the medications or services mentioned in this article.