Valaciclovir

What is Valaciclovir?

Valaciclovir contains the active ingredient valaciclovir and belongs to a group of medicines called antivirals. The medication treats several conditions, including cold sores. Cold sores are caused by the herpes simplex virus (HSV), most commonly HSV-1. While Valaciclovir can help manage outbreaks, especially when started early, it does not cure the herpes simplex virus.

What is Valaciclovir 500mg Used For?

In addition to treating herpes simplex virus, Valaciclovir also works against varicella zoster (VZV) and cytomegalovirus (CMV). This makes it suitable for treating:

• Shingles (in adults)
• HSV infections of the skin
• Genital herpes
• Recurrent HSV infections of the eye

Valaciclovir 500mg tablets can also be used to prevent infection with CMV after organ transplants.

What are Cold Sores?

Cold sores are small, fluid-filled blisters that develop on or around the lips. They can be painful and usually begin with itching, burning or tingling in the affected area before the blisters appear. A cold sore is contagious from the first signs of an outbreak, such as tingling or itching, until it fully heals. To reduce the risk of spreading the virus, avoid kissing and oral sex during this period. Avoid touching the cold sore unnecessarily, and wash your hands with soap and water after touching it or applying treatment.

Once you have contracted HSV, the virus remains in your body for life. It lies dormant in nearby nerve cells and can reactivate, causing further outbreaks. Antiviral medication can help treat outbreaks and may reduce their severity or duration, but it cannot eliminate the virus.

Common cold sore triggers include:

• Having another infection
• Fever
• Stress
• Tiredness and fatigue
• Injury to the affected area
• Menstruation
• Strong sunlight

Not everyone experiences the same triggers, and outbreaks can occur without an obvious cause.

How Does Valaciclovir Work?

Valaciclovir converts into the active form, aciclovir, in the body. It works by inhibiting the enzyme the virus needs to grow and multiply in the body's cells. This helps the body's immune system fight the infection and push it back into remission.

You can find more information about aciclovir on the NHS website.

How Long Does Valaciclovir Take to Work?

Valaciclovir starts working against the herpes virus soon after you take it, however, you may not notice an improvement in your cold sore for some time. It is recommended to start taking the medication at the earliest signs of an outbreak.

How to Take Valaciclovir for Cold Sores

Always take Valaciclovir tablets exactly as prescribed by your clinician or doctor. Your dose will depend on why the medication was prescribed for you. Your prescriber will discuss this with you.

To treat cold sores, take 2,000 mg (four 500 mg tablets) twice a day. The second dose should be taken 12 hours (no sooner than 6 hours) after the first dose.

You should take valaciclovir for one day (two doses) only. Take the tablets with water and swallow them whole.

Dose Adjustment

Your prescriber may adjust your valaciclovir dose if you are over 65 years of age, have a weak immune system, or have kidney problems. Talk to your clinician or doctor before taking the medication if any of these apply to you.

If You Forget to Take Valaciclovir

If you forget to take Valaciclovir, take it as soon as you remember, unless it is almost time for your next dose. In this case, just skip the missed dose. Do not try to double-dose to make up for one you have forgotten.

If You Take Too Many Valaciclovir Tablets

Valaciclovir is usually not harmful unless you take too much over several days. If this happens, you may feel sick, vomit, experience kidney problems, feel confused, agitated, or less aware, or become unconscious. Talk to your clinician or doctor if you take too much Valaciclovir, and take the package with you to in-person appointments.

Valaciclovir Side Effects

Like all medications, Valaciclovir can cause side effects, though not everyone will experience them. It's recommended to understand what could occur before starting treatment.

Possible Valaciclovir side effects include:

More details on potential Valaciclovir side effects are in the Patient Information Leaflet enclosed with the medication. If you experience any adverse reactions, you can report them to your clinician or use the MHRA's Yellow Card scheme.

Serious Side Effects of Valaciclovir

Rarely, Valaciclovir tablets can cause severe allergic reactions (anaphylaxis). This can result in rapid development of symptoms including:

• Flushing, itchy skin rash
• Swelling of the lips, face, neck, and throat, causing breathing difficulties
• Fall in blood pressure, leading to collapse

Skin rashes or redness may also occur and may appear with or without blisters. Skin irritation, oedema, and fever/flulike symptoms can also happen.

If you experience any of the above side effects, stop taking Valaciclovir and seek immediate medical attention.

Valaciclovir Warnings and Interactions

Although Valaciclovir 500mg tablets are effective for cold sores, the treatment may not be suitable for everyone. You should not take the medication if you:

• Are allergic to valaciclovir, aciclovir, or any of the other ingredients
• Have previously developed an extended rash associated with fever, enlarged lymph nodes, increased liver enzyme levels, and/or eosinophilia after taking valaciclovir

Precautions Before Taking Valaciclovir

Speak to your clinician or doctor before starting Valaciclovir if you:

• Have liver or kidney problems
• Are over 65 years of age
• Have a weak immune system

If you are unsure whether any of the above applies to you, seek medical advice.

Valaciclovir and Other Medicines

It's important to tell your clinician or doctor if you are taking, have recently taken, or might take any other medicines. This includes any over-the-counter or herbal remedies.

You should especially seek medical advice if you are taking other medicines that affect the kidneys, including:

• Aminoglycosides
• Organoplatinum compounds
• Iodinated contrast media
• Methotrexate
• Pentamidine
• Foscarnet
• Ciclosporin
• Tacrolimus
• Cimetidine
• Probenecid

Pregnancy and Breastfeeding

Valaciclovir 500mg is usually not recommended for use during pregnancy. If you are pregnant, think you could be pregnant, or are planning on having a baby, don't take the medicine without speaking to your doctor.

Your doctor will weigh up the benefit to you against the risk to your baby of taking Valaciclovir while you're pregnant or breastfeeding.

Frequently Asked Questions About Valaciclovir for Cold Sores