Cold Sores / Valacyclovir


Generic Valtrex

Valacyclovir is the generic form of the brand Valtrex®. Both medications work similarly in the body.

Valacyclovir is an antiviral medication that is used to treat oral herpes and genital herpes, which are caused by herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). It can also be used to treat varicella zoster virus (VZV).

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Transparent manufacturing

Valacyclovir manufactured by Camber, Cadista, and Cipla in India

For herpes, valacyclovir can be used to prevent outbreaks or to treat initial or recurrent outbreaks although suppressive therapy for oral herpes (cold sores) is an off-label treatment. Valacyclovir starts to work immediately in the body. Exact dosage and timing of the medication depends on how you are using it and whether you have HIV.

1 in 10 people may experience side effects including dizziness, vomiting, diarrhea, skin reactions after exposure to sunlight (photosensitivity), rash, and itching (pruritus). More serious side effects are rarer and may require medical attention.

What is valacyclovir (Valtrex®)?

Valacyclovir is an antiviral drug used to treat oral herpes (also known as cold sores) and genital herpes caused by herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). It is also used to treat varicella zoster virus (VZV), the virus that causes chickenpox and shingles. It is also sometimes used for cytomegalovirus (CMV) and Bell's Palsy, but these uses are not FDA-approved and are considered “off-label”. Physicians on the Dapper platform prescribe valacyclovir for the treatment of genital herpes and oral herpes only. If you feel that you need valacyclovir for any other condition, please seek in-person care. Note that valacyclovir is not an antibiotic. Antibiotics fight bacteria whereas antivirals are active against viruses, which are technically not even alive.

Valacyclovir can be used to treat genital herpes and oral herpes in several ways, depending on the goal. It can be used to:

  • Treat initial and recurrent outbreaks of genital herpes
  • Treat initial and recurrent outbreaks of oral herpes
  • Prevent outbreaks of genital herpes
  • Prevent outbreaks of oral herpes (an “off-label” use)
  • Decrease the risk of transmitting herpes to a partner by decreasing viral shedding (viral shedding is when the virus is found on the skin or mucous membranes. This can occur without symptoms and is called asymptomatic shedding)

Valacyclovir was initially FDA-approved to treat herpes simplex infections in 1995 as the brand name drug Valtrex®, and has been used since then with a decreasing the risk of spreading genital herpes to an uninfected partner. If you suffer from recurrent outbreaks of oral or genital herpes, your doctor may prescribe valacyclovir to treat or suppress outbreaks.

How does valacyclovir work?

Herpes viruses are basically just DNA wrapped in a protein coating. In order for the virus to be able to multiply, it needs to first replicate its DNA. Valacyclovir acts through multiple mechanisms to prevent the replication of herpes DNA. It is active against HSV-1, HSV-2, VZV, and to a lesser extent other herpes viruses, like CMV. When viral DNA is prevented from replicating, the virus cannot multiply and infect uninfected cells. This is how valacyclovir works:

  • Aborts (stops) or shortens outbreaks of genital herpes, oral herpes, and shingles
  • Prevents outbreaks of genital and oral herpes
  • Decreases the risk of viral transmission to the uninfected partner

Valacyclovir vs. acyclovir

Acyclovir was the first antiviral drug for the treatment of herpes infections. Acyclovir was initially FDA-approved to treat herpes simplex infections in 1985 as the brand name drug Zovirax® and was found to be very effective for treating herpes infections. The main problem with acyclovir is that only 10%-20% of it is absorbed from the digestive tract. To make matters worse, higher doses have worse absorption than lower doses. This made it very difficult to maintain a high enough level of the drug in the blood to be effective, requiring patients to take up to five doses per day.

Valacyclovir is considered a prodrug of acyclovir, which means that it is converted into acyclovir in the body. Since valacyclovir is absorbed much better than acyclovir (54% for valacyclovir vs 10%-20% for acyclovir), it can be dosed less frequently and get equal or better results compared to acyclovir. Valacyclovir is dosed from 1 to 3 times daily, depending on what it's being used for, whereas acyclovir is used 2 to 5 times daily depending on the indication. Valacyclovir is generally preferred by doctors and patients because it is easier to dose and may be more effective.

How long does it take for valacyclovir to work?

Once in the blood, valacyclovir starts to work almost immediately. Since it specifically attacks the DNA replication process, it will only attack herpes viruses that are reproducing; so while it starts to work on an active infection very quickly, it will not fight the virus that is inactive and hiding in the nervous system.

Nevertheless, if taken on a daily basis it may reduce the number of outbreaks a person might experience by50%. Taken at the earliest feelings that an outbreak is on the verge of occurring, valacyclovir may either abort the attack or shorten how long it will last. Remember, with valacyclovir treatment for herpes, the earlier you take it after the symptoms appear, the better.

While it goes to work within hours of taking the medication, the symptoms and sores of an actual outbreak may take days to begin to heal and the virus can stay active throughout the healing process.

Valacyclovir dosages

Valacyclovir comes in two doses, 500 mg and 1,000 mg tablets. Although there are only two doses, there are several different ways to use the medicine for different indications. Below is a summary of how to use valacyclovir. Keep in mind that these doses may need to be changed for people with specific conditions, such as kidney problems. If you're prescribed valacyclovir, take it according to your prescriber's instructions.

Oral herpes

Abort (stop) an outbreak at the earliest sign or symptom (prodrome)

It's important to take the medicine at the first sign or symptom because there is no evidence that the medication works once lesions are visible. Most people will be able to tell when an outbreak is coming on. They may experience burning, itching, tingling, or other sensations that alert them to an imminent outbreak.

Take two tablets of valacyclovir 1,000 mg (2,000 mg total) followed by another two 1,000 mg tablets 12 hours later. Make sure to stay hydrated by drinking fluids throughout the day. For those who are HIV-infected, the recommended dose is 1 gram (1000 mg) every 12 hours for 5 to 10 days.

Treatment with suppressive therapy

Valacyclovir is not approved for suppressive therapy of oral herpes, but doctors have the discretion to prescribe it for this use if they believe that it is an appropriate course of treatment for a particular patient. This is considered off-label treatment. It is up to the medical judgment of the doctor to decide if off-label treatment is appropriate for a patient based on the patient's unique medical history, symptoms, and preferences. Physicians who choose to prescribe valacyclovir off-label for the suppression of oral herpes may recommend 500 mg or 1,000 mg once daily.

Genital herpes

Treatment of initial genital outbreak

To treat an initial episode of genital herpes, the FDA recommends taking valacyclovir 1 gram (1000 mg) twice a day for 10 days starting at the first sign or symptom of lesions, preferably within 48 hours of onset. The CDC recommends this same dose for 7 to 10 days; “treatment may be extended if healing is not complete after 10 days.” For HIV-infected patients, they recommend 1 gram (1000 mg) every 12 hours for 5 to 14 days.

Treatment of recurrent genital herpes, including HIV-infected patients

The FDA recommends using 500 mg of valacyclovir twice daily for 3 days starting at the first sign or symptom of lesions-preferably within 24 hours of onset. The CDC also recommends valacyclovir 500 mg twice daily for 3 days, but adds an alternative regimen of valacyclovir 1 g (1000 mg) one time a day for 5 days. Valacyclovir 1 g taken every 12 hours for 5 to 14 days is recommended by the HIV guidelines.

Treatment with suppressive therapy

People with less than 10 outbreaks per year should take valacyclovir 500 mg once daily. Valacyclovir 1,000 mg once daily is recommended for people with 10 or more outbreaks per year.

To prevent transmission to a partner

The infected partner should take valacyclovir 500 mg once a day to decrease the risk of transmission to the uninfected partner. The data are strong but refer to patients with 9 or fewer outbreaks each year.

Valacyclovir side effects

What follows is a summary and does not include every side effect possible. Please, read the package insert for a comprehensive list of side effects

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

Common (may affect up to 1 in 10 people): feeling sick, dizziness, vomiting, diarrhea, skin reaction after exposure to sunlight (photosensitivity), rash, itching (pruritus)

Uncommon (may affect up to 1 in 100 people), feeling confused, seeing or hearing things that aren't there (hallucinations), feeling very drowsy, tremors, feeling agitated. These nervous system side effects usually occur in people with kidney problems, the elderly or in organ transplant patients taking high doses of 8 grams or more of valacyclovir a day. They usually get better when valacyclovir is stopped or the dose reduced.

Other uncommon side effects: shortness of breath (dyspnea), stomach discomfort, rash, sometimes itchy, hive-like rash (urticaria), low back pain (kidney pain), blood in the urine (hematuria)

Uncommon side effects that may show up in blood tests: reduction in the number of blood platelets, which are cells that help blood to clot (thrombocytopenia), reduction in the number of white blood cells (leukopenia), increase in substances produced by the liver

Rare: (may affect up to 1 in 1,000 people): unsteadiness when walking and lack of coordination (ataxia), slow, slurred speech (dysarthria), fits (convulsions), altered brain function (encephalopathy), unconsciousness (coma), confused or disturbed thoughts (delirium). Like the nervous system side effects listed above, these side effects also usually occur in people with kidney problems, the elderly or in organ transplant patients taking high doses of 8 grams or more of valacyclovir a day (higher than the maximum doses used for any indication). They usually get better when valacyclovir is stopped or the dose reduced.

Other rare side effects: kidney problems where you pass little or no urine.
Severe allergic reactions (anaphylaxis): These are rare in people taking valacyclovir. Anaphylaxis is marked by the rapid development of flushing, itchy skin rash, swelling of the lips, face, neck, and throat-causing difficulty in breathing (angioedema), fall in blood pressure leading to collapse. If any of these occur, get emergency treatment immediately.

Important safety information