Aciclovir

Treatment for genital herpes with aciclovir

Aciclovir 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 available as tablets and is used either to treat individual outbreaks (episodic treatment) or taken daily to reduce the frequency of recurrences (suppressive therapy). Aciclovir is a well-established treatment with an extensive safety record and is recommended by the British Association for Sexual Health and HIV (BASHH) as a first-line antiviral for genital herpes.

Access aciclovir 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 aciclovir.

What is aciclovir?

Aciclovir is an antiviral medicine belonging to the nucleoside analogue class. It works by interfering with the ability of the herpes simplex virus to replicate, reducing the severity and duration of outbreaks and, when taken as suppressive therapy, significantly lowering the frequency of recurrences.

Aciclovir does not cure genital herpes. The herpes simplex virus remains in the body permanently once acquired, but aciclovir can help manage the condition effectively. It is supplied as tablets and is taken orally.

What is the active substance in aciclovir?

The active substance is aciclovir. Once absorbed, aciclovir is converted into its active form inside virus-infected cells. It then inhibits the viral enzyme DNA polymerase, which the herpes simplex virus needs to reproduce. By blocking this enzyme, aciclovir prevents the virus from replicating and spreading to surrounding tissue, reducing the severity and duration of an outbreak.

Because the activation of aciclovir occurs preferentially in virus-infected cells, it has a targeted action with limited effect on healthy cells.

Who is the treatment suitable for?

Aciclovir for genital herpes may be considered for adults following a medical assessment. It may be appropriate for:

• Adults experiencing a first episode of genital herpes
• Adults with recurrent outbreaks who wish to reduce their severity and duration
• Adults experiencing frequent recurrences (typically six or more per year) who may benefit from daily suppressive therapy
• Adults who wish to reduce the risk of transmitting the virus to a sexual partner

Treatment is not suitable for everyone. A full medical assessment is required before prescribing, and your UK-registered prescriber will determine whether aciclovir is appropriate for your individual circumstances.

What dosages are used?

The dosage of aciclovir depends on whether it is being used for episodic treatment or suppressive therapy.

First episode of genital herpes:
400 mg three times daily for five days, or 200 mg five times daily for five days. Treatment should ideally begin within 72 hours of symptoms appearing for maximum benefit.

Recurrent episodes (episodic treatment):
400 mg three times daily for three to five days, started at the first sign of an outbreak.

Suppressive therapy:
400 mg twice daily, taken continuously. Your UK-registered prescriber will review the ongoing need for suppressive therapy at regular intervals, typically after 12 months of use.

Your UK-registered prescriber will confirm the most appropriate dosage and treatment approach for your circumstances.

How does aciclovir work?

Aciclovir works by targeting the herpes simplex virus's ability to reproduce. After being absorbed by the body, it is taken up preferentially by cells infected with the herpes simplex virus, where it is converted by a viral enzyme into its active form. This active form then inhibits the viral DNA polymerase, the enzyme the virus uses to copy its genetic material and produce new viral particles.

By blocking this process, aciclovir reduces the number of viral particles produced, limiting the spread of the virus within the body and reducing the severity, duration, and symptoms of an outbreak.

How is aciclovir taken?

Aciclovir tablets are taken orally. The following guidance helps ensure the treatment is as effective as possible.

• Take each dose at regular intervals throughout the day as directed by your prescriber
• Tablets can be taken with or without food
• Drink plenty of water during treatment to stay well hydrated, particularly if you are taking higher doses
• Complete the full course even if symptoms improve before the course is finished
• For suppressive therapy, take the tablets at the same times each day to maintain consistent blood levels

Sexual contact during treatment

During an active outbreak, sexual contact should be avoided until the sores have fully healed. Genital herpes can be transmitted even when no visible symptoms are present (asymptomatic shedding), so the use of condoms between outbreaks can reduce but does not eliminate the risk of transmission.

When should aciclovir not be used?

Aciclovir should not be used if:

• You have a known allergy to aciclovir, valaciclovir, or any of the other ingredients listed in the patient information leaflet
• You have severe kidney impairment without appropriate dose adjustment under prescriber supervision

Before starting treatment, inform your UK-registered prescriber of your full medical history, any allergies, and all medicines you are currently taking, including over-the-counter medicines and supplements. Dose adjustments may be required for people with kidney impairment or certain other health conditions.

What side effects can occur?

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

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

• Nausea
• Vomiting
• Diarrhoea
• Abdominal discomfort
• Headache
• Dizziness
• Fatigue
• Skin rash or itching

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

• Sensitivity to sunlight
• Raised liver enzymes (usually detected on blood tests)
• Mild kidney function changes

Rare side effects:

• Neurological effects including confusion, agitation, or drowsiness, more commonly associated with higher doses or in people with kidney impairment

If you experience a severe allergic reaction, including swelling of the face, lips, tongue or throat, difficulty breathing, or a severe skin reaction, stop taking aciclovir and seek emergency medical help immediately.

If you notice any side effects, inform your UK-registered prescriber.

Reporting side effects

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

Aciclovir active substance and excipients

Active substance:
Aciclovir 200 mg or 400 mg per tablet, depending on formulation.

Other ingredients vary by manufacturer and formulation.
Please refer to the patient information leaflet supplied with your medication for a full list of excipients.

• Aciclovir patient information leaflet