Valtrex is most commonly used to treat various forms of the herpes virus including genital herpes, shingles and cold sores. It assists the body’s immune system in fighting the virus and preventing reoccurrence. More information

A doctor will review your order and write you a prescription, if appropriate. This prescription is then forwarded to a pharmacy. The pharmacy will have your medicine delivered to you within one to three working days. Read more about this process here.

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Valtrex is the brand name for the medicine valaciclovir which is used to treat viral infections, particularly genital herpes (herpes simplex), shingles (herpes zoster) and cold sores (herpes labialis). Valtrex stops the viruses growing, multiplying and infecting more cells in the body. It is also used to prevent viruses from returning.  

This is a prescription-only medication and comes in tablet form. The main active ingredient is valaciclovir. The body breaks down valaciclovir to produce aciclovir. 

What is Valtrex?

Valtrex is most commonly used to treat various forms of the herpes virus including genital herpes, shingles and cold sores. It assists the body’s immune system in fighting the virus and preventing reoccurrence. It is not a cure for the virus as a cure does not currently exist. It can stop the development of the virus, however, once contracted the virus continues to live in the body and can reactivate at any time. Valtrex can prevent this from happening so can be used to prevent future recurrence of the viruses. 

Valaciclovir is the active ingredient in Valtrex and the body breaks it down into two substances: aciclovir and valine (an amino-acid).  Aciclovir is an anti-viral medicine. The body converts aciclovir to an active form that blocks an enzyme known as DNA polymerase that the body needs to produce DNA. This blocking means the virus cannot develop and spread.  

Amino acids are essential compounds of the body. There are certain amino acids that the body needs to develop and function correctly. Valine is one of these, which are known as essential amino acids. 

Valtrex is the common brand name. Other brand names are: Talavir, Valaciclovir Allen, Valaciclovir Biogaran, Valaciclovir GSK, Valaciclovir Sandoz, Valaciclovir Winthrop, Valavir, Valherpes, Valtrex S, Virval and Zelitrex. 

When is Valtrex used?

Valtrex is commonly used to treat genital herpes, shingles and cold sores.  These conditions can be extremely painful and uncomfortable and Valtrex can relieve the symptoms. However, it is not a cure as the virus remains in the body once contracted. Genital herpes is a sexually transmitted infection (STI) that can be caught through sexual intercourse (vaginal, anal and oral). It can be avoided by using a condom during sex. Symptoms of genital herpes include: 

  • Blisters around your sexual organs, buttocks or thighs 
  • A burning, tingling or itching sensation in these areas 
  • Pain on urinating 
  • Unusual vaginal discharge in women  

There is no cure for genital herpes and once you have it you may experience further outbreaks for the rest of your life.  But Valtrex can treat the symptoms that prevent future reoccurrences of this viral infection. However, if you have genital herpes, just because you are taking Valtrex this does not mean you will not pass the virus on to your partner. Therefore, it is important to always practice safe sex. You should not have sexual contact if you have open blisters or sores. If you suspect you have genital herpes you should talk to a doctor as Valtrex is a prescription-only medicine. If you regularly suffer from herpes your doctor may prescribe Valtrex to take as soon you recognize the symptoms of this virus. 

Shingles is also referred to as herpes zoster and is a viral infection. It is a painful rash that turns into blisters. Shingles is linked to chickenpox as both are caused by the varicella-zoster virus (which is why Valtrex can be used to treat chickenpox). Cold sores are painful blisters that appear on the mouth and lips. 

Valtrex can also be used to prevent a CMV (cytomegalovirus) infection after organ transplant. This is a common virus, linked to the herpes virus, that is not usually dangerous. However, it can cause a serious infection for people who have a weak immune system as their bodies will find it harder to fight infection. Valtrex is also used to prevent and treat HSV (herpes simplex virus) eye infections which are also caused by the herpes virus.  

How do you use Valtrex?

At the first signs of genital herpes, shingles or cold sores it is essential to see a doctor. The sooner medication is prescribed and taken the sooner it will be effective. Any delay in taking medication can make the symptoms worse. However, you can contract the herpes virus without realising you have it as it can lie dormant in the body for several months or even years. Symptoms of the virus occur when it activates, develops and spreads. The symptoms will appear when the virus has developed significantly.  This is why it is important to consult a doctor as soon as you suspect you may have the herpes virus. Valtrex can help prevent the virus from developing. If this is the first treatment of Valtrex for genital herpes it will be most effective if taken within 24 hours of the first symptoms appearing. 

Valtrex treats the initial symptoms and can also help prevent future outbreaks of the different herpes viral infections. If this is not the first time you have experienced the herpes virus you are likely to recognize the symptoms (blisters, itchy skin, fever, feeling sick, pain while urinating). If this is the case you should start treatment as soon as possible to prevent the viral infection becoming worse. It is important to complete the course of treatment even when the symptoms subside as this will help prevent the viral infection recurring in the future.  You should notice your symptoms are improving with a reduction in the itching and blistering. If this has not happened after you have finished the course of Valtrex treatment you should speak to your doctor. 

Valtrex comes in tablet form and should be taken with water. It is important to take this medicine at the same time every day and to complete the course of tablets you are prescribed. Taking the medicine at regular and even intervals gives the most effective results. The usual course of this medicine is between three and ten days – your doctor will decide how long you need to take Valtrex depending on the severity of your symptoms. Sometimes a longer course may be prescribed to avoid reinfection. 

What dosages are there?

Valtrex comes in different strengths, most commonly 250mg and 500mg. How much you should take will depend on your individual situation.  When prescribing Valtrex your doctor will take into account:  

  • Which virus you have (genital herpes, shingles, or cold sores) 
  • How severe the virus is 
  • Your age 
  • If you have a weak immune system 
  • If you have liver or kidney disease 
  • If you are taking any other medication (be sure to inform your doctor of any medication you are taking: even herbal products) 
  • Any allergies you have (including to aciclovir) 

Valtrex can be taken by men, women and children over 12 with signs of the herpes virus. The most common dosages for adults and children over 12 years are: 

  • Genital herpes: one 500mg tablet or two 250mg tablets twice a day. If this is the first time you have had the virus the usual dosage is taken for five days or for up to ten days. If this is not the first time you have had the virus the usual dosage is for three-five days. 
  • Shingles: 1000mg three times a day (therefore two 500mg tablets three times a day). The most common time period to treat shingles with Valtrex is for seven consecutive days. 
  • Cold sores: 2000mg twice a day (therefore four 500mg tablets twice a day). The second dose should be taken twelve hours after the first and no sooner than six hours. For cold sores, Valtrex is usually taken for one day only (two doses). 

For the dosages for the treatment of the other viral infections mentioned above please refer to the product leaflet. 

What are the side effects of Valtrex?

The most common side effects of taking Valtrex can be headaches nausea, vomiting, dizziness, and stomach problems. Headaches are particularly common. However, you could also experience other side effects such as: 

  • Diarrhoea 
  • Rashes and itching 
  • Confusion/agitation 
  • Sensitivity to light 
  • Tremors 
  • Hallucinations 
  • Disturbed thoughts 
  • Shortness of breath 
  • Drowsiness 
  • Blood in the urine 
  • Unsteadiness whilst walking/lack of coordination 
  • Slow/slurred speech 
  • Fits 

If any of these occur after taking Valtrex consult a doctor. 

When shouldn’t you use Valtrex?

Do not use this medicine if you are allergic to aciclovir or any of the ingredients in it. Do not take other medicines containing aciclovir while taking Valtrex (read the ingredients of any other medicines you may be taking and inform your doctor you are taking them). This could affect the effectiveness of the Valtrex. It is essential you inform your doctor if you have liver or kidney problems. As with all medicines, tell your doctor what you are already taking (including herbal medicines) before taking Valtrex. 

Valtrex is not recommended for pregnant or breastfeeding women. It is advisable to stop drinking alcohol while you are taking Valtrex as it could make the side effects worse. If Valtrex makes you dizzy or drowsy do not drive or operate machinery as this could cause a serious accident. 

Does Valtrex interact with other medication?

Yes, Valtrex can interact with other medication so it is essential you inform your doctor of any other medication you are taking.  Other medicines could affect the effectiveness of Valtrex or cause a serious medical reaction. 

Where can you buy Valtrex?

Valtrex is a prescription-only medicine and is not available over the counter. You must obtain a prescription from your doctor to buy Valtrex.  

Can I get Valtrex without a prescription?

No, you must have a prescription to take Valtrex. 




Package Leaflet: VALTRES 250 mg 500MG FILM-COATED TABLETS Retrieved April 21, 2019 from 

Valtrex (n.d). Retrieved 21 April, 2019 from 

Valtrex (n.d). Retrieved 21 April, 2019 from 

Assessed by:

Dr Imran Malik, General practitioner
Registration number: GMC: 4741365

Dr Imran Malik studied undergraduate medicine at King's College University in Central London and clinical studies at the prestigious King's College Hospital. He graduated with a MBBS degree in 2000 and went on to gain postgraduate memberships with the Royal Society of Medicine and also General Practice in 2006.