What is Valtrex?

Valtrex contains valaciclovir, an antiviral medicine used to treat cold sores (herpes labialis) caused by the herpes simplex virus (HSV-1). It works by stopping the virus from multiplying, which helps reduce symptoms such as tingling, pain and itching and allows sores to heal more quickly.

What is Valtrex Used For?

Valtrex 500 mg is prescribed to treat cold sores in adults and adolescents aged 12 years and over.
While valaciclovir is licensed for other conditions (for example genital herpes, shingles and prevention of cytomegalovirus after transplant), these uses are outside the scope of this product page.

How Valtrex Works?

After you swallow Valtrex, valaciclovir is converted to aciclovir, which is then changed into its active triphosphate form. This active form blocks an enzyme called viral DNA polymerase, preventing the herpes virus from copying its genetic material and spreading.

Starting treatment at the very first sign of a cold sore helps limit the outbreak and shorten healing time.

Cold Sores: Symptoms, Treatment, and Healing Tips

Symptoms: A tingling, itching or burning sensation is usually followed by small fluid-filled blisters around the lips or face. Cold sores are contagious from the first tingle until the skin has completely healed, typically within about 10 days.

Treatment Options: Cold sores can heal on their own, but antiviral treatments help reduce discomfort and speed up recovery. Oral antivirals such as Valtrex are effective when started early. Pain-relieving gels or creams and sun-protective lip balms can also help.

Healing Tips: Protect lips with a balm containing SPF 15 or higher, keep hands clean, avoid kissing or sharing cups and cutlery while sores are present, eat soft foods if lips are sore, and stay well hydrated.

Can you buy Valtrex 500 mg over the counter?

No. In the UK Valtrex is a prescription-only medicine (POM). You need a consultation with a registered prescriber, such as your 123Meds prescriber to ensure it is safe and appropriate before it can be supplied.

Alternative Medications

If Valtrex is not suitable, other prescription antivirals can also treat cold sores:

Aciclovir – taken several times a day and works in the same way, but requires more frequent dosing.

These options are available only on prescription. Your prescriber can advise which treatment best fits your needs.

How to take Valtrex

For cold sores only (short-course treatment):

Adults: Take 2,000 mg (four 500 mg tablets) twice in one day, 12 hours apart.

Start the first dose as soon as you feel the early symptoms such as tingling, burning or itching.

Swallow the tablets whole with a full glass of water. Drink plenty of fluids throughout the day to protect kidney function.

If you miss a dose on that same day, take it as soon as you remember. If the day has passed, do not double the dose—seek advice from your prescriber.

Active ingredient: Valaciclovir hydrochloride.

Inactive ingredients may vary by manufacturer but typically include: microcrystalline cellulose, crospovidone (Type A), povidone (K-90), magnesium stearate, and a film coating of hypromellose, macrogol, polysorbate 80, titanium dioxide (E171) and indigo carmine aluminium lake (E132).

Always check the patient information leaflet (PIL) in your pack for the full ingredient list — especially if you have allergies or sensitivities.

Most people tolerate Valtrex well. Common side effects include headache, nausea, abdominal pain, diarrhoea, dizziness and tiredness.

Seek urgent medical help from A&E by calling 999 if you notice:

• Signs of an allergic reaction (difficulty breathing, swelling of the face, lips, tongue or throat)
• Confusion, hallucinations or unusual agitation
• Very little or painful urination, swelling of the feet or ankles, or shortness of breath (possible kidney effects)

Staying well hydrated lowers the risk of kidney problems.