What is Valaciclovir?

Valaciclovir is an antiviral medicine used to treat and suppress genital herpes (HSV-1 and HSV-2) in adults.
It is converted to aciclovir in the body, which stops the herpes virus from multiplying.
Compared with standard aciclovir tablets, valaciclovir provides the same effectiveness with fewer daily doses.

What is Valaciclovir Used For?

Treatment of genital-herpes outbreaks – shortens the length and severity of an episode and speeds healing.
Suppressive therapy – taken daily to reduce how often outbreaks occur and to lower (but not eliminate) the risk of passing the virus to a partner.

How Valaciclovir Works

After swallowing, valaciclovir is changed into aciclovir.
Aciclovir blocks the viral DNA polymerase enzyme, preventing the herpes virus from making new copies of itself.
This limits the infection, shortens outbreaks and reduces recurrences, but it does not remove the virus from the body.

Key Considerations Before Taking Valaciclovir

Medical history: Tell your prescriber if you have kidney disease or any other significant health condition.
Kidney safety: Drink plenty of water and inform your doctor about all other medicines you take, especially any that can affect the kidneys.
Start promptly: Begin treatment as soon as you notice early signs (tingling, burning or blisters) for best results.
Transmission: You can still pass genital herpes to others while taking valaciclovir. Use condoms and avoid sexual contact during outbreaks.

Storage: Keep tablets below 25 °C in a dry place, away from light and out of the reach of children.

Can you buy Valaciclovir over the counter?

No. Valaciclovir is a prescription-only medicine (POM) in the UK.

A registered prescriber must review your symptoms and medical history before it can be supplied.

Alternative Medications

Aciclovir – works in the same way but usually requires more frequent dosing.
Valtrex – the original brand name for valaciclovir.

Your prescriber can help choose the best option.

Treatment of an outbreak

Recurrent episode: 500 mg twice daily for 3 days (or 1 g once daily for 5 days if advised).

Suppressive (preventive) therapy

500 mg once daily

Take tablets with or without food, swallow whole with a full glass of water and stay well hydrated.

If you miss a dose, take it as soon as you remember unless it is nearly time for the next one.

Do not double up doses.

Active ingredient: Valaciclovir hydrochloride.

Inactive ingredients vary by manufacturer but typically include microcrystalline cellulose, crospovidone, povidone, magnesium stearate, and a film coating of hypromellose, macrogol, polysorbate 80, titanium dioxide (E171) and indigo carmine aluminium lake (E132).

Please note, ingredients may vary by manufacturer and reading the patient information leaflet supplied is important prior to commencing treatment. 

Common: headache, nausea, abdominal pain, diarrhoea, dizziness, tiredness.

Rare but serious: allergic reaction (swelling of face or throat, difficulty breathing), confusion, hallucinations, or signs of kidney problems such as reduced or painful urination or swelling of ankles/feet.

Seek medical attention immediately from your GP, NHS111 or A&E if you experience serious or persistent symptoms.

Drinking plenty of fluids helps lower the risk of kidney problems.