Reviewed by Dr Samantha Miller MB ChB
(2017, University of Glasgow)
GMC number: 7561464
Information last reviewed 24/01/2021
Valaciclovir is an antiviral drug used to treat infections caused by herpes simplex viruses. It is used to treat genital herpes, cold sores and shingles. It works fast to relieve the symptoms of an outbreak, and can also be used long-term to suppress outbreaks.
Valaciclovir can be used to treat oral herpes (cold sores), genital herpes, shingles and chickenpox.
People experiencing recurrent outbreaks of genital herpes or cold sores may choose to take valaciclovir tablets for a period of 6–12 months to reduce the risk of outbreaks. When used in this way, viral shedding is also reduced, which means you will be less contagious. However suppressive therapy with valaciclovir does not guarantee you will not still experience outbreaks and it does not eliminate viral shedding completely.
Valaciclovir works best to treat symptoms when taken within 2–3 days of symptom onset, and should be started within 5 days. Symptoms usually start to improve within 3 days of taking valaciclovir, however, sores can take up to 3 weeks to completely disappear. Future outbreaks of herpes tend to be shorter in duration and less severe. Use of valaciclovir when symptomatic can shorten the duration of symptoms by 1–2 days.
Valaciclovir reduces the frequency, severity and duration of outbreaks of herpes. As herpes is most contagious when symptoms are present, the use of valaciclovir will reduce the risk of transmission of the virus to others. However herpes can be transmitted even when symptoms are not present, so the use of valaciclovir does not eliminate the risk of transmission.
It is recommended to avoid sexual contact while genital lesions are present, and avoid kissing while oral lesions are present.
Dose |
Genital herpes - 500mg, taken twice per day for 5 days Cold sores - two doses of 2000mg, 12 hours apart Shingles - 1000mg, taken three times a day for 7 days |
Type of Medicine | Antiviral |
Mechanism |
Inhibits viral DNA replication by competitively binding to viral DNA polymerase, as well as inserting itself into replicated viral DNA and terminating the string |
Available Size |
10, 20, 30, 42 or 84 tablets |
Available Strengths |
500mg |
Active Ingredient |
Valaciclovir |
Price |
From £1.13 per tablet |
Side Effects |
Can include dizziness, diarrhoea, nausea, vomiting, photosensitivity reactions of the skin, itching, rash, confusion, drowsiness |
Valaciclovir is the active ingredient in valaciclovir tablets
The inactive ingredients in valaciclovir tablets may include microcrystalline cellulose, crospovidone, povidone, magnesium stearate and silica colloidal anhydrous.
Please note: different brands may contain different inactive ingredients.
The dosage of valaciclovir that you should take will depend on what you are being treated for. For genital herpes, the usual dosage is 500mg taken twice a day for a duration of five days. To treat cold sores the usual dose is two doses of 2000mg 12 hours apart. For shingles, the usual dose is 1000mg taken three times a day for 7 days.
Always take valaciclovir as your doctor has prescribed it. You should start your treatment as soon as possible. Valaciclovir tablets should be swallowed whole with a glass of water and you should try and take it at the same time each day. You should try to complete the entire course of medication prescribed to you. If you miss a tablet, take it as soon as you remember, however, if it is only a few hours until your next dose, skip the missed dose. Do not take a ‘double dose’ to make up for a missed dose. If you are unsure, speak to your doctor.
Common side effects include:
Rarer side effects include:
If you experience any severe side effects or symptoms of an allergic reaction (breathing difficulties, swelling, itching, hives, rash) you should seek immediate medical attention.
If you experience any prolonged side effects you should speak to the prescribing doctor.
Drinking plenty of water will help to prevent side effects from occurring. If you get an upset stomach, it is even more important to stay hydrated. If you get headaches you can take painkillers such as paracetamol to ease the discomfort.
You should not use valaciclovir if you are allergic to valaciclovir or aciclovir. If you are taking any other medication, if you are pregnant or breastfeeding, or if you have any other health conditions, particularly kidney or liver problems, you should inform the prescribing doctor as this medication may not be suitable. You should also inform the prescribing doctor if you are over the age of 65, or have a weakened immune system.
You should inform your doctor if you are taking, have taken or are planning on taking any other medications, including non-prescription (over the counter) medications, herbal remedies, vitamins or recreational drugs.
Valaciclovir is not known to be harmful during pregnancy, but due to a lack of clinical evidence, it is not usually recommended during pregnancy. If you are pregnant, there is a chance you may be pregnant, or you plan on becoming pregnant you should disclose this to the prescribing doctor.
Aciclovir is passed into the breast milk of breastfeeding women. It is not thought to be harmful to the infant, however is not recommended to breastfeeding women. If you are breastfeeding it is important to disclose this to the prescribing doctor.
Herpes does not always require treatment and in fact most cases can be managed at home without medication prescribed by a doctor. There are measures you can take yourself to help your body to heal:
Valaciclovir does not cause thrush. The symptoms of vaginal thrush commonly include itching, discomfort, redness and a white lumpy or creamy discharge. If you experience symptoms of thrush while you are using valaciclovir then ask your doctor for advice as you will need a separate treatment for it.
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