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Tablets for cold sores

Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 3 minutes read

Cold sores, caused by the herpes simplex virus (HSV), are a common and often recurrent ailment that affects millions of people worldwide. While various topical creams and home remedies can provide relief, many individuals turn to tablets or oral medications for a more systemic approach to managing cold sores.

Two commonly used antiviral medications are available in tablet form to treat cold sores. Acyclovir and valacyclovir tablets are prescription-only antiviral medicines used occasionally to treat persistent cold sores. They do not cure a cold sore (herpes simplex virus) infection but help reduce the outbreak's severity and length. In people with frequent outbreaks and those with a weak immune system, acyclovir and valacyclovir tablets can be used to help reduce the number of future outbreaks as a preventative medication.

Doctor’s advice

Who is it for?

The effectiveness of cold sore tablets can vary among individuals and depends on factors such as the timing of medication initiation and the frequency of outbreaks. Studies have shown that initiating antiviral treatment at the earliest signs of a cold sore can reduce the severity and duration of symptoms. However, these medications are most effective when taken regularly for individuals experiencing frequent outbreaks. When treating cold sores with acyclovir or valaciclovir tablets, you should take your prescribed dose as soon as you recognize the tingling or burning sensation at the site of the outbreak, ideally within 5 days.

The earlier taken, the more effective in stopping the virus in its tracks.

You might recognize triggers – stress and exposure to the cold or sun are common ones.

How does it work?

Acyclovir and valacyclovir are antiviral agents that interfere with the growth and replication of viral particles, helping your immune system target and tackle the virus. In the body, valacyclovir is metabolized into acyclovir.

Prescribed treatments are best to be used in the initial stages of an outbreak, usually within the first five days. For treatment of outbreaks, you will take a high dose for a short course, usually five days. Doses vary depending on your age and kidney function. If you have a weakened immune system, treatment doses are usually double the standard dose for healthy individuals. Suppressive antiviral treatment is an option for frequent (usually six or more during the year) cold sore outbreaks causing distress or if outbreaks are affecting your social life. In healthy adults, treatment of your first outbreak with acyclovir tablets involves a course of 200 mg five times per day for five days or 500 mg twice a day for five days with valacyclovir tablets.

Should anyone avoid taking it?

Do not take acyclovir or valacyclovir tablets if you have previously experienced an allergic reaction to acyclovir or any ingredients used to make acyclovir tablets.

Are there any side effects?

Acyclovir and valacyclovir are generally well tolerated by most individuals. A small number of patients may experience fatigue, headache, dizziness, nausea, vomiting, abdominal pain, itching, and a rash (including sensitivity to light).

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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