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Drug Info

What is Valtrex?

Cropped SingleCare logo By | April 26, 2020
Medically reviewed by Karen Berger, Pharm.D.

Experiencing outbreaks of cold sores, shingles, or genital herpes can be uncomfortable to deal with both physically and emotionally. These are all examples of herpes virus infections that can be treated with antivirals. Valtrex is an antiviral medication that could help treat all three of these conditions. Here, we discuss what Valtrex is, why it’s prescribed, proper dosages, side effects, and compare it to similar drugs.   

What is Valtrex?     

Valtrex is a prescription antiviral medication that’s used to treat herpes virus infections, including cold sores, genital herpes, shingles, and chickenpox. It can’t cure herpes infections, but Valtrex can treat symptoms like herpes sores and blisters. If you have a herpes infection like shingles, you’ll need a prescription from a doctor in order to buy Valtrex. 

Valtrex is the brand name of a generic medication called valacyclovir hydrochloride. These medications are chemically the same, work the same way, and are equally effective at treating herpes virus infections. As an antiviral drug, Valtrex works by slowing down the growth and spread of viruses. There are many companies that manufacture generic valacyclovir, but the brand name Valtrex is manufactured by GlaxoSmithKline. Brand-name versions of medications tend to be more expensive than generic versions.     

What is Valtrex used for?

Valtrex is prescribed by doctors to treat herpes virus infections. It can help relieve symptoms that come from herpes virus type 1 (HSV-1) and herpes virus type 2 (HSV-2). It can also help relieve symptoms from the varicella zoster and herpes zoster viruses. It’s important to know that Valtrex can’t cure viruses, it can only treat symptoms and stops the virus from multiplying and further affecting healthy cells.   

Viruses cause infections that are uncomfortable to experience, and many people who have the herpes simplex virus, varicella zoster, or herpes zoster virus will have painful blisters or sores. Here are some of the infections that Valtrex can help treat:  

  • Cold sores (herpes labialis)  
  • Chickenpox (varicella)
  • Shingles (herpes zoster)  
  • Genital herpes 

Cold sores

Caused by the herpes simplex virus, cold sores are commonly experienced by children and adults. Also known as “fever blisters,” cold sores appear on the outside of the mouth and lips. As the herpes virus spreads, it damages the skin and leaves fluid-filled blisters, which are contagious and can spread from person-to-person by direct contact. Treatment of cold sores often involves taking an antiviral like Valtrex at the first sign of symptoms.      


Caused by the varicella zoster virus, chickenpox mainly affects young children under the age of 10. It’s easily identified by its itchy, blistery rash that appears all over the body, and is considered to be highly contagious. Valtrex can help bring symptomatic relief to children with chickenpox.


Shingles manifest as a painful, blistery rash that often appears on one side of the body. If someone’s had chickenpox, the varicella zoster virus that caused it still lives in their body. The virus can flare up again later in life, causing shingles. Shingles can be very painful and can lead to other complications as well. Older adults are the most common age group to experience shingles, but younger people can get shingles, too. Valtrex helps minimize the pain, rash, and blisters that come from having shingles. Read SingleCare’s shingles treatment and medications to learn more about shingles.     

Genital herpes

Herpes viruses 1 and 2 cause genital herpes, which is considered to be a sexually transmitted disease (STD) that spreads by vaginal, anal, or oral sex. Genital herpes is contagious, so direct or sexual contact of any kind during an outbreak should be avoided. Outbreaks are characterized by the appearance of genital pain and sores. Even if you aren’t having an outbreak, safer sex practices like using a condom properly (although it is important to note that condoms may not fully protect you) can help keep genital herpes from spreading to others. Valtrex can help genital herpes sores go away quicker and help treat recurrent genital herpes for immunocompetent adults.     

Valtrex dosages

If you have a herpes simplex or varicella zoster virus infection, the amount of Valtrex you’ll need to take will vary depending on your individual symptoms and age. Valtrex tablets are most common, but it’s also available as a liquid suspension. Your doctor will prescribe the right form of Valtrex for you when he or she writes your prescription. For the best results, Valtrex should be taken as soon as possible after symptoms start, so do not delay in contacting your healthcare provider.

The following table lists standard doses of Valtrex for adults: 

Cold Sores Shingles Genital herpes
2 grams taken twice daily for 1 day taken 12 hours apart 1 gram taken 3 times per day for 7 days 1 gram taken twice daily for 10 days

These dosages are general guidelines. Your doctor may ask you to take Valtrex more or less frequently depending on what type of infection you have and how severe your symptoms are. It’s safe to take Valtrex every day as long as you’ve been instructed to do so by your doctor.

Here are the standard doses of Valtrex for children with cold sores or chickenpox:  

Cold Sores Chickenpox 
Age Patients 12 years and older Patients 2 years to less than 18 years
Standard dosage 2 grams taken twice daily for 1 day taken 12 hours apart Varies based on weight

Maximum dose is 1 gram taken 3 times daily for 5 days

How long does it take Valtrex to clear up an outbreak?

Taking Valtrex with a full glass of water helps make sure your kidneys can process it efficiently. Valtrex starts working to treat symptoms right away. Even though it starts working right away, it may take several days for you to notice a difference in your symptoms. Valtrex stays in the body for about 24 hours after ingestion and is eliminated from the system if another dose isn’t taken.       

It can take up to 10 days for Valtrex to start working. The amount of time it takes your symptoms to go away will depend on your age, the severity of your symptoms, and your metabolism. However, symptom relief from Valtrex is not a cure for herpes simplex or varicella zoster viruses.         

If you miss a dose of Valtrex, you should take the next dose as soon as possible. Taking your missed dose as soon as you remember you’ve missed it will help keep your herpes infection from worsening. If it is almost time for your next dose, just resume the schedule and do not take a double dose.      

Keep Valtrex at room temperature, away from direct sunlight, and out of the reach of children, who might accidentally mistake it for candy or food. If your child accidentally takes Valtrex, you should seek medical advice immediately.     


Even though Valtrex is very effective at treating herpes virus infections, it shouldn’t be taken by everyone. You should talk with your doctor before taking Valtrex if you have any of the following medical conditions:  

  • Kidney problems or kidney disease. People with kidney problems or kidney disease can potentially experience a worsening of symptoms if they use Valtrex.   
  • HIV/AIDS. Having HIV suppresses the immune system, increasing the probability of getting other medical conditions. People with HIV or AIDS who take Valtrex greatly increase their risk of a serious blood disorder called thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS).  
  • Kidney or bone marrow transplants. If you’re taking Valtrex and are about to have a bone marrow or kidney transplant, you should talk with your doctor. Your risk of getting TTP/HUS will greatly increase if you take Valtrex during your transplant process. 

If you’re pregnant and are considering taking Valtrex, you should talk with your doctor to learn how Valtrex might affect your pregnancy. You might not be able to take the medication at all. It’s possible for Valtrex to pass from mothers to infants via breast milk, and there is no data on the effects of this. Talking with your doctor before breastfeeding your baby is the best way to avoid any harm. 


Taking Valtrex at the same time as certain other medications may cause side effects to worsen or cause additional health problems. You should talk with your healthcare provider before taking Valtrex if you’re taking any of the following medications: 

  • Varicella virus vaccine
  • Zoster virus vaccine
  • Foscarnet 
  • Acyclovir
  • Nephrotoxic agents 
  • Bacitracin 
  • Methotrexate 
  • Cancer medications
  • Arthritis medications 
  • Medications used to prevent organ transplant rejections 

The best way to learn more about Valtrex and any potential drug interactions is to talk with your healthcare provider. Bringing a complete list of all the prescription drugs you’re taking will help them decide if Valtrex is right for you. 

What are the side effects of Valtrex?

Taking Valtrex may cause side effects that feel uncomfortable. If you’re taking Valtrex, here are some possible side effects you might experience:  

  • Headache
  • Stomach pain/abdominal pain 
  • Nausea
  • Vomiting 
  • Dizziness
  • Tiredness
  • Trouble sleeping
  • Trouble concentrating
  • Loss of appetite  
  • Skin rash  
  • Diarrhea  
  • Joint pain 

Although it’s rare, Valtrex can cause more serious side effects that might require medical attention. If you’re taking Valtrex and start to have hallucinations, aggressive behavior, or seizures, you should contact your doctor right away. Valtrex might also cause confusion and speech problems that require a doctor’s attention.

Taking Valtrex very rarely causes kidney problems or kidney failure that could potentially be life-threatening. If you have kidney problems you should talk to your doctor before taking Valtrex. 

As stated earlier, Valtrex can also cause a rare blood disorder called thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS). This blood disorder can be very serious and potentially life-threatening and is more of a risk for immunosuppressed patients that have an underlying health condition like HIV or AIDS. 

The best way to learn more about any side effects you might experience from taking Valtrex is to talk with your doctor or healthcare provider. 

Are there alternatives to Valtrex?

There is no over-the-counter version of Valtrex, but some people take the generic version of Valtrex, valacyclovir. Valtrex isn’t the only antiviral medication that can treat herpes virus and varicella zoster virus infections. If someone is allergic to Valtrex or has an underlying medical condition that prevents him or her from taking it, a doctor may recommend another antiviral.  

Here are some alternative medications to Valtrex: 

  • Acyclovir is a generic medication used to treat herpes simplex and varicella zoster viruses. It’s available in generic form or under the brand name Zovirax. It treats the same conditions as Valtrex, but its bioavailability is lower, which means that lower concentrations of it are absorbed by the body. Learn more about the difference between acyclovir and Valtrex here.     
  • Famciclovir is a generic medication typically used to treat varicella zoster virus infections like shingles. Also known under the brand name Famvir, famciclovir is a good alternative to Valtrex for people with compromised immune systems.   

Home remedies for herpes

In addition to taking medication, many people treat their herpes virus infections with natural and home remedies. Natural remedies shouldn’t be a substitute for antiviral drugs, but many people find that they help heal painful sores and blisters.  

Here are some natural and home remedies that could possibly help your herpes virus infection:  

  • Drinking echinacea tea. Echinacea is an herb. Echinacea tea can boost the immune system, helping the body fight off virus outbreaks that manifest as cold sores, shingles, genital herpes, or chickenpox. 
  • Using hydrogen peroxide for cold sores. Hydrogen peroxide can clean cold sores and help them heal faster because of its antiseptic properties. 
  • Eating foods rich in L-lysine. Some studies suggest that the amino acid L-lysine can help keep the herpes virus from replicating. Taking a lysine supplement or eating foods that contain L-lysine like vegetables, legumes, and fish can help keep your herpes virus infection from worsening.
  • Applying cool compresses. For genital herpes, applying a cool compress to the affected area can help alleviate pain and itching that come from sores and blisters.  

The best way to learn more about possible alternatives to Valtrex is to talk with your doctor or healthcare provider. There’s no one size fits all medication or treatment plan that’s best for everyone.