Valaciclovir

List of topics

• What is valaciclovir and how is it used for the treatment of genital herpes?
• Access valaciclovir following an online medical consultation
• How does valaciclovir work?
• Who is the treatment suitable for?
• What dosages are used?
• How does valaciclovir compare to aciclovir?
• Sexual contact during treatment
• Who should not take valaciclovir
• What side effects can occur?
• Reporting side effects
• Are there any interactions to be aware of?
• Valaciclovir active substance and patient information leaflet

What is valaciclovir and how is it used for the treatment of genital herpes?

Valaciclovir is a prescription-only antiviral medicine used in adults for the treatment of genital herpes, an infection caused by the herpes simplex virus (HSV). It is a prodrug of aciclovir: once swallowed, it is converted rapidly and almost completely into aciclovir, the active antiviral substance. This conversion is more efficient than with standard aciclovir tablets, which is why valaciclovir can usually be taken less often. It is used either to treat individual outbreaks (episodic treatment) or taken daily to reduce how often outbreaks happen (suppressive therapy).

Access valaciclovir following an online medical consultation

Start the online consultation and complete the medical questionnaire. A UK-registered prescriber will review your answers and, where appropriate, issue a prescription for valaciclovir. Your medication will be dispensed by a GPhC-registered pharmacy and delivered to your door.

How does valaciclovir work?

Genital herpes is caused by a virus that spreads by multiplying inside infected cells. Once valaciclovir converts to aciclovir in the body, it acts inside those infected cells and stops the virus from copying itself. This slows the infection down, helping outbreaks clear up faster and easing symptoms.

Valaciclovir doesn't get rid of the virus completely. Genital herpes stays dormant in the body between outbreaks, which is why it can flare up again later. Taking valaciclovir as suppressive therapy doesn't cure it either, but it can make flare-ups happen much less often.

Who is the treatment suitable for?

Valaciclovir may be considered for adults with a first episode or recurrence of genital herpes, those experiencing frequent recurrences who may benefit from suppressive therapy, and those wishing to reduce the risk of transmission to a partner. It is also licensed for herpes labialis (cold sores) and herpes zoster (shingles, including ophthalmic zoster) in immunocompetent adults. A full medical assessment is required before prescribing, and your UK-registered prescriber will confirm suitability.

What dosages are used?

Dosing depends on whether treatment is for a first episode, a recurrence, or suppression, and may be adjusted for reduced kidney function.

• First episode: typically 500mg twice daily, sometimes extended to ten days as first episodes can be more severe.
• Recurrent episodes: typically 500mg twice daily for three to five days, started as early as possible, ideally at the first sign of tingling or itching.
• Suppressive therapy: typically 500mg once daily, sometimes as a divided dose for very frequent recurrences. Ongoing need is usually reviewed every six to twelve months.

Your UK-registered prescriber will confirm the appropriate dose and duration for you.

How does valaciclovir compare to aciclovir?

Valaciclovir and aciclovir work in the same way, since valaciclovir converts into aciclovir in the body. The main difference is dosing frequency: valaciclovir's improved absorption usually allows once or twice-daily dosing, while standard aciclovir is taken more often. Neither is considered more effective than the other; the choice is generally based on tolerability and how easily a dosing schedule fits your routine.

Sexual contact during treatment

Avoid sexual contact during an active outbreak until sores have fully healed. HSV can be transmitted even without visible symptoms, so condom use between outbreaks reduces but does not eliminate the risk. Suppressive therapy also reduces, but does not eliminate, the risk of passing the virus to a partner.

Who should not take valaciclovir

Valaciclovir should not be used if you have a known hypersensitivity to valaciclovir, aciclovir, or any of the tablet's other ingredients. Caution and dose adjustment may be needed if you have reduced kidney function, as aciclovir is cleared via the kidneys, and both kidney impairment and older age increase the risk of certain neurological side effects. Valaciclovir should only be used in pregnancy if the benefits outweigh the risks, and only used while breastfeeding when clinically necessary. Tell your UK-registered prescriber your full medical history and current medicines before starting.

What side effects can occur?

As with all medicines, valaciclovir can cause side effects, although not everyone will experience them.

Very common (may affect more than 1 in 10 people):

• Headache

Common (may affect up to 1 in 10 people):

• Nausea, vomiting, or diarrhoea
• Dizziness
• Skin rashes, including increased sensitivity to sunlight

Uncommon (may affect up to 1 in 100 people):

• Confusion or hallucinations, more often seen with kidney impairment or in older adults, and generally reversible once treatment stops

This is not the complete list; refer to the patient information leaflet for full details.

Seek urgent medical help for signs of a severe allergic reaction, such as facial or throat swelling or difficulty breathing, or if you notice a severe skin reaction alongside fever, as this can rarely indicate DRESS (a serious drug reaction).

Reporting side effects

Suspected side effects can be reported to the MHRA via the Yellow Card scheme.

Are there any interactions to be aware of?

Because aciclovir is cleared via the kidneys, valaciclovir should be used with caution alongside other medicines that affect kidney function or are cleared the same way, including certain antibiotics (aminoglycosides), ciclosporin, tacrolimus, methotrexate, foscarnet, and pentamidine. Cimetidine and probenecid can also raise aciclovir levels in the blood. Tell your prescriber about all medicines and supplements you take.

Valaciclovir active substance and patient information leaflet

Active substance: valaciclovir hydrochloride, equivalent to 500mg valaciclovir per tablet. Other ingredients vary by manufacturer; see the PIL for the full list. The current UK valaciclovir patient information leaflet is available via the Electronic Medicines Compendium. The leaflet in your pack may differ slightly if updated or from another brand.

This page is general information only and does not replace the PIL or individual medical advice.