Aciclovir Tablets

Buy aciclovir 400mg tablets (Zovirax) for quick and effective genital herpes treatment

  • Antiviral medication used to treat genital herpes

  • Can be used as a longer-term preventative treatment

  • Available from £14.99 + prescription fees and delivery costs

Our prices

Strength Quantity Price Stock
400mg15 tablets£14.99In Stock
400mg30 tablets£19.99In Stock
400mg45 tablets£23.99In Stock
400mg168£34.99In Stock
Prices exclude a prescription fee. This treatment requires a quick online consultation,
which a doctor will review to determine if a prescription is appropriate.

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Dr Samantha Miller

Reviewed by Dr Samantha Miller MB ChB
(2017, University of Glasgow)
GMC number: 7561464

Information last reviewed 12/02/2021


What is aciclovir?

Aciclovir is an antiviral medication used to treat infection caused by herpes viruses, including cold sores, genital herpes, chickenpox and shingles. It is available on prescription as an oral medication, or as a topical cream which can be bought over the counter, prescription-free. It can also be used as a long-term suppressive therapy to reduce the frequency, duration and severity of outbreaks of symptoms.

Aciclovir for herpes prevention

People experiencing recurrent outbreaks of genital herpes or cold sores may choose to take aciclovir tablets for a period of 6–12 months to reduce the risk of symptomatic outbreaks. When used in this way, viral shedding is also reduced, which means you will be less contagious. However suppressive therapy with aciclovir does not guarantee you will not still experience outbreaks and does not eliminate viral shedding completely.

How long does it take for aciclovir to work?

When taken for symptomatic relief, aciclovir is most effective if taken within 48–72 hours of the onset of symptoms, and should be started within 5 days. Symptoms usually start to subside within 3 days of taking the medication, however, the sores caused by initial herpes infection can take up to three weeks to completely disappear. Recurrent outbreaks of herpes tend to be much shorter in duration. Use of aciclovir can shorten the duration of an outbreak by 1–2 days. 

When taken as a long-term suppressive therapy, significant suppression of viral replication and shedding is achieved within 5 days. However, it is important to know that viral shedding is not completely eliminated by the use of aciclovir, so you may still be able to pass on the virus. 

Am I still contagious when taking aciclovir?

Aciclovir reduces the frequency, severity and duration of outbreaks of herpes. As herpes is most contagious when symptoms are present, the use of aciclovir will reduce the risk of transmission of the virus to others. However herpes can be transmitted even when symptoms are not present, so it is important to be aware that aciclovir does not eliminate the risk of transmission. Therefore, it is recommended that you avoid sexual contact while genital sores are present, and avoid kissing while oral sores are present.

Aciclovir summary


200mg, 5 times per day

Type of Medicine



Competitively inhibits and inactivates viral DNA processes, preventing replication

Available Size

15, 30, 45 or 168 tablets

Available Strengths


Active Ingredient



From 21p per tablet

Side Effects

Can include nausea, vomiting, diarrhoea, headaches, stomach pains, feeling dizzy, feeling tired, fever, itching, skin rash


Active ingredients

The active ingredient in aciclovir tablets is aciclovir - an antiviral agent.

Inactive ingredients

The inactive ingredients of aciclovir tablets may include: magnesium stearate, microcrystalline cellulose, sodium starch glycollate, pregelatinised starch and colloidal anhydrous silica.

Please note: different brands of aciclovir may contain different inactive ingredients

Which ingredients can cause an allergic reaction?

Aciclovir can cause a severe allergic reaction in people presenting as facial/lip swelling, a rash/hives, severe dizziness and trouble breathing. However, the incidence of a severe allergic reaction is rare. However, if you notice any of the symptoms listed above after taking this anti-retroviral drug, please visit your local emergency department to get immediate medical attention.


How to take aciclovir tablets

You should start your treatment as soon as possible. Aciclovir tablets can be swallowed whole with water. If you have trouble swallowing the tablets, they can be dissolved in a glass of water and stirred before drinking. Aciclovir should be taken for a minimum of five days, and for the duration recommended by the prescribing doctor. 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.

Aciclovir dosage

For the treatment of an initial outbreak or recurrence of oral or genital herpes, the usual dose is 200mg five times per day. This is usually recommended for a duration of 5 days. 

When used for suppression of oral or genital herpes, the usual dose is 200mg four times per day. This is usually continued for 6–12 months.

Can aciclovir tablets be split or crushed?

Yes, aciclovir can be split, crushed or dispersed in water. 

Is there a dispersible aciclovir available?

If you struggle to swallow aciclovir tablets, they can be dispersed in a glass of water. One 200mg tablet should be dissolved in at least 50ml of water, stirred and swallowed.

Side Effects

Aciclovir side effects

Common side effects of aciclovir tablets include:

  • Stomach pain
  • Diarrhoea
  • Dizziness, particularly on standing up
  • Tiredness (fatigue)
  • Headache
  • Nausea
  • Skin reactions after exposure to light (photosensitivity)
  • Rash
  • Vomiting
  • Itching
  • Hives

Rare side effects of aciclovir tablets are:

  • Allergic reaction (breathing difficulty, swelling, itching, hives, rash, collapse)
  • Anaemia (reduced number of red blood cells)
  • Agitation
  • Fever
  • Confusion
  • Kidney problems (e.g. passing less urine than normal)
  • Breathing difficulties
  • Neurological problems
  • Seizures, fits (convulsions)
  • Drowsiness
  • Hallucinations
  • Jaundice
  • Changes in the blood

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.


You should not use aciclovir if you are allergic to aciclovir or valaciclovir. 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.

Drug interactions

You should inform the prescribing doctor if you are taking, have taken or are planning on taking any other medications, including over the counter (non-prescription) medications, herbal remedies and recreational drugs.

Aciclovir and pregnancy/breastfeeding

Aciclovir is not known to be harmful during pregnancy and is often prescribed to pregnant women for the treatment or suppression of herpes. However, 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, if you are breastfeeding and require aciclovir, it is important to disclose this to the prescribing doctor.

Treatment Options

Aciclovir tablets vs aciclovir cream

Aciclovir is available as a topical cream, which can be purchased over the counter without a prescription. Topical creams may be useful for the self-management of oral herpes, but are not recommended for the treatment of genital herpes and should not be used in the vagina or anus. 

Oral aciclovir tablets are only available on prescription and are recommended for use for the treatment or suppression of oral and genital herpes.  

Non-prescription alternatives

Herpes does not necessarily require treatment and the vast majority of cases can be managed at home without prescription medication. There are several measures you can take at home to help your body to heal:

  • Topical antiviral cream, available over the counter without prescription may be useful for oral herpes but is not recommended for treatment of genital herpes. Topical antiviral creams should not be used inside the mouth, vagina or anus.
  • Use of a mild local anaesthetic cream may be useful, particularly in the case of genital herpes where sitting or urinating may be particularly painful.
  • Oral painkillers such as paracetamol and ibuprofen can be used for pain relief.
  • Keep the area clean, gently cleansing the area with water. 
  • Apply an ice pack wrapped in a flannel to the area, which can help soothe the pain. Never apply an ice pack directly to the skin.
  • If urinating is particularly painful during an outbreak of genital herpes, try passing urine in the shower, or pouring warm water over the area while urinating.
  • Wash your hands before and after using topical antiviral or anaesthetic creams. 
  • Wash your hands before and after any contact with the affected area, both to prevent spreading the virus to other areas, and to prevent the introduction of further infection from the hands.
  • In genital herpes, avoid wearing tight clothing and synthetic fibres, and instead choose loose-fitting underwear made from natural fibres e.g. cotton.
  • Avoid sexual until symptoms of genital herpes have cleared completely.
  • Avoid kissing and sharing cutlery and cups until symptoms of oral herpes have cleared completely.
  • If you think you might have herpes, you should get tested as soon as possible.
  • It is important to inform sexual partners if you have a history of genital herpes, as this can be transmitted even when symptoms are not present.


Is aciclovir an antibiotic?

Aciclovir is not an antibiotic. Antibiotics are used to treat bacterial infections. Herpes is a viral infection and aciclovir is an antiviral medication. 

Can aciclovir treat HPV?

Human papillomavirus (HPV) infection typically causes warts, including genital warts. It does not cause genital herpes. Aciclovir will not treat HPV infection as the virus replicates in a different way from the herpes simplex viruses that cause herpes infection. 

If you are worried you may have genital warts, you should see your doctor for diagnosis and treatment. You can also be tested for infection with HPV even if you have no symptoms.

Some strains of HPV are associated with the development of cancers such as cervical cancer, anal cancer and some oral and throat cancers. To reduce the risk of these cancers, the UK NHS introduced a nationwide HPV vaccination programme to school children and at-risk adults. Adults can also obtain the vaccination using a private prescription.

Can aciclovir treat shingles?

Shingles is caused by another type of human herpesvirus, the varicella-zoster virus, and results in a painful skin rash. Aciclovir can be used to treat shingles, however, the dose is usually different to that used for oral or genital herpes. In shingles, aciclovir is most effective when taken within the first 72 hours of symptoms. 

If you think you have shingles, it is important to contact your doctor for an accurate diagnosis and treatment.

Will aciclovir affect a drug test?

Aciclovir can be found in blood and urine when a person is taking the drug, and for several days after completing treatment. As aciclovir is excreted by the kidneys into the urine, it may affect levels of other drugs also processed in this way. There is no evidence that taking Aciclovir will cause you to test positive for substances such as opiates, cannabinoids, alcohol, amphetamines, benzodiazepines or cocaine. If you are taking aciclovir and are worried about drug testing, speak to the prescribing doctor for more information.

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