Valacyclovir (Oral)

Valacyclovir, also known by the brand name Valtrex, is a drug taken in oral form to treat infections caused by the herpes virus including herpes labialis, herpes zoster and herpes simplex in adults, as well as chickenpox and cold sores in children.


What is Valacyclovir?

Valacyclovir is an anti-viral drug, which means it stops the growth of certain viruses or infections caused by the virus, in this case herpes. While Valacyclovir does not cure the virus, it does decrease the severity of symptoms on the body, as well as the length of the viral outbreak. While the symptoms are eased, most patients find it easier to allow their bodies to fight off the virus. Patients treated with Valacyclovir find that the sores which appear with the onset of the herpes virus heal much faster and that new sores do not form as the virus runs its course. The pain and itching associated with the viral outbreak is also lessened when on Valacyclovir.

When used on children under 12 years of age and at least 2 years of age, Valacyclovir is effective against the symptoms caused by the chickenpox virus as well as cold sores that could potentially become severe.

Valacyclovir is also effective in the chronic suppressive treatment therapy of recurrent genital herpes episodes in adults that are immonosupressed or HIV-1 infected. While there is an indication of reduced transmission of genital herpes adults who are taking Valacyclovir, it is not typically prescribed for this purpose and detailed studies are not available. For this reason, patients with recurrent genital herpes are advised to practice safe sex to avoid spreading the virus by contact.

How does Valacyclovir work?

Valacyclovir works to interfere with the reproductive cycle of the herpes virus by preventing the replication of the DNA necessary for the virus to multiply. The drug stops the virus from multiplying and spreading itself to the healthy cells nearby. Valacyclovir is known as a “prodrug”, which means that it is not itself active until it is transformed by the body to acyclovirin, which is the active agent that fights the viruses.

While Valacyclovir is not a cure for shingles, cold sores, genital herpes or chicken pox, it does help heal the sores that are a result of the infection of the herpes virus as well as relieve the pain, discomfort and other symptoms caused by the virus while the body fights to get rid of the virus itself.

Valacyclovir is prescribed to patients in caplet form. The coated, blue pills may be taken with meals, but this is not essential. Pills are available in 500 milligram and 1 gram doses and the dose prescribed is dependent upon the patient's health details, the severity of the disease and symptoms.

Valacyclovir should be prescribed as soon as possible after the first onset of infection. Most patients experience relief from symptoms in two or three days with healing of the sores in about a week. Valacyclovir may also be used for suppressive therapy in patients who have repeated outbreaks and are familiar with the signs enough so that they can begin their doses immediately.

What is suppressive therapy?

Suppressive therapy is the term used to describe a course of medication that is used as a preventive measure to prevent the symptoms or full-on outbreak of a disease. In the case of Valacyclovir, patients may want to discuss a daily dose of the drug with their doctor as a form of suppressive therapy. Typically patients who experience more than six outbreaks per year are urged to consider suppressive therapy with Valacyclovir to prevent outbreaks and symptoms. With suppressive therapy, the number of outbreaks per year can be reduced by 70 to 80% in patients who carry the virus.

Conditions treated

  • Herpes labialis
  • cold sores
  • herpes zoster
  • shingles
  • herpes simplex
  • genital herpes
  • chicken pox
  • cold sores

Type of medicine

  • Antiviral

Side Effects

Side effects of Valacyclovir experienced most commonly by patients under treatment include:

  • Nausea and vomiting
  • Diarrhea
  • Headache
  • Sad, empty, discouraged feelings
  • Poor appetite
  • Loss of interest or pleasure in daily life
  • Fatigue
  • Lack of concentration
  • Insomnia or fitful sleep
  • Cramps

Obviously, if any of these side effects continue beyond what is considered normal or beyond the treatment period or if they become severe, they should be reported to your healthcare professional immediately.

Other patients may experience the following side effects, but they are very rare. If any of these side effects are experienced while in treatment with Valacyclovir, notify your doctor immediately:

  • Aggressive behavior
  • Confusion
  • Unsteady or shaky feeling
  • Hallucinations
  • Speech problems
  • Seizure or convulsions
  • Kidney side effects such as diminished urination, painful urination, swollen feet or ankles
  • Fever
  • Shortness of breath
  • Unusual bleeding such as nosebleeds or bleeding gums
  • Red or pink urine
  • Rash that is unrelated to the virus sores
  • Stomach pain, bloody diarrhea, vomiting
  • Swollen face, hands or feet
  • Increased heart rate
  • Depression



Adults and children below two years of age being treated for chickenpox receive a dosage of Valacyclovir that is determined by their doctor. In children from two to 18 years of age, the dose is based on body weight and is typically 20 milligrams per kilogram of body weight, which is directed to be taken three times per day for five days. Under normal circumstances, the dose is not usually more than 1,000 milligrams three times per day but the doctor will determine each patient's dose based on circumstances.

Cold sores

Adults being treated for cold sores with Valacyclovir are most commonly prescribed a 2,000 milligram dose every 12 hours for one day. Children over 12 years of age receive the same dose as adults but children below 12 years of age will have a lower dose as determined by the treating physician.

Genital herpes – first outbreak

Genital herpes patients experiencing their first outbreak of the virus are typically given a dose of Valacyclovir as part of their treatment that is 1,000 milligrams two times a day over the course of 10 days. Children being treated for this virus will have their dose of Valacyclovir determined by their medical professional.

Genital herpes – recurrent outbreaks

As recurrent outbreaks are common with the herpes virus, adults who are on a course of treatment for them are typically prescribed 500 milligrams two times per day for three days. Children with recurrent outbreaks of the herpes virus will have their dose determined by their doctor at the beginning of treatment.

Suppressive therapy – genital herpes

Adults on suppressive therapy for genital herpes outbreaks will be prescribed a maintenance dose of 500 milligrams or 1,000 milligrams of Valacyclovir once per day, depending on the severity of the recurrence experienced by the patient and the treating physician's recommendation. Children on suppressive therapy will have their dosage determined by their medical professional.


Patients experiencing shingles outbreaks will often have a dose of 1,000 milligrams of Valacyclovir as their course of treatment. Children's dosage of Valacyclovir for shingles symptoms vary and are prescribed by their doctor at the time of treatment.

Missing dose

If a dose of Valacyclovir is missed, it should be advised that the patient take it as soon as the missed dose is realized, unless it is close to the time for another dose. Then, the regular dosing schedule should be kept and the missed dose should be skipped in favor of double dosing.


As with all drugs, patients who are being treated with a course of Valacyclovir for any reason should inform their healthcare professional of any allergies or pre-existing conditions. Additionally, recent treatments, as well as hereditary disease and condition information, should be disclosed to your physician prior to treatment with this or any drug. Informing your health care professional of any prescription or non-prescription medication you are taking as well as any herbal or holistic supplements or treatments is required for safety and effectiveness.

Specifically, if you have ever had kidney or liver disease or problems with your immune system, informing your doctor before taking Valacyclovir is essential. Notifying your doctor if you have HIV (human immunodeficiency virus infection) or AIDS (acquired immunodeficiency syndrome) is absolutely imperative. Patients who have undergone bone marrow transplantation or kidney transplantation may have an increased risk of severe side effects and should inform their physician of these conditions if a course of Valacyclovir is being considered for treatment.

If you are pregnant or planning to become pregnant or are breast-feeding, inform your healthcare professional prior to taking Valacyclovir. If, while on a course of treatment with Valacyclovir, you become pregnant, tell your doctor as soon as possible.

Discuss the use of alcohol and tobacco with your doctor prior to being treated with a course of Valacyclovir. Use of alcohol and tobacco could diminish the effectiveness or cause unwanted side effects when taken in combination with Valacyclovir.

Certain drugs should not be used together in case of interaction, so your physician may prescribe different dosing amounts of schedules depending on any drugs you are currently taking. The following medicines are known to have adverse interactions with Valacyclovir and should be discussed with your healthcare professional before taking in tandem:

  • Abacavir
  • AccessPak for HIV PEP Expanded with Kaletra
  • AccessPak for HIV PEP Expanded with Viracept
  • Amikin
  • Ampicillin
  • Apriso
  • Asacol
  • Atripla
  • Azulfidine
  • Baraclude
  • Benemid
  • Canasa
  • Carboplatin
  • Cidofovir
  • Cimetidine
  • Combivir
  • Conray
  • Cyclosporine
  • Demerol
  • Dipentum
  • Eloxatin
  • Entecavir
  • Famciclo
  • Folex PFS
  • Foscarnet
  • Fosphenytoin
  • Garamycin
  • Gastrografin
  • Gentamicin
  • Giazo
  • Hecoria
  • Hepsera
  • Hexabrix
  • Hypaque
  • Iodamide
  • Iohexol
  • Ipodate
  • Isovue
  • Kitabis Pak
  • Lamivudine
  • Lialda
  • Measles virus vaccine
  • Mematine
  • Meperidine
  • Meperitab
  • Meprozine
  • Methotrexate
  • Mycophenolate Mofetil
  • Mycophenolic Acid
  • Namenda
  • Neo-Tab
  • Neomycin
  • Omnipaque (various)
  • Oxilan
  • Paromycin
  • Phenytoin
  • Probenecid
  • Rapamune
  • Regurin
  • Renovist
  • Rheumatrex
  • Rowasa
  • Salofalk
  • Sandimmune
  • Sulfasalazine
  • Tagamet
  • Talimogene Laherparepvec
  • Tizanidine
  • Trospium
  • Ultravist
  • Urografin
  • Valproic Acid
  • Zostavax

This list is not complete, so consult with your health care professional and disclose any drugs, vitamins or herbal supplements you may be taking to see if there are any adverse interactions with Valacyclovir.


Patients with advanced HIV-1 disease, as well as bone marrow transplant and rental transplant recipients, have experienced thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) while under clinical trials of Valacyclovir. Treatment should be stopped immediately if any side effects or symptoms of TTP/HUS occur when taking Valacyclovir.

Acute rental failure has been reported in elderly patients, patients with underlying renal diseases, patients receiving other drugs and patients without adequate hydration while being treated with a course of Valacyclovir.

Adverse reactions by the central nervous system in some patients being treated with Valacyclovir have also been reported in adults and children. Typically these patients have some underlying renal disease, which is why medical conditions and history should always be reported to your healthcare professional prior to receiving treatment with Valacyclovir or any other drug.

Patients being treated with Valacyclovir are encouraged to maintain adequate hydration by drinking plenty of water and not becoming overheated or overexerted.

Valacyclovir has not been shown to be effective in reducing the transmission of sexually transmitted infections with the exception of HSV-2. Patients with sexually transmitted infections are encouraged to observe safe sexual practices.

The effects on pregnancy, reproduction and the effect of taking Valacyclovir revealed no evidence of risks; however the weight of the potential benefits of treatment of this drug against the potential risk to the fetus or fertility should be discussed with your healthcare professional.

Studies performed on nursing mothers exhibited signs of Valacyclovir in breast milk and therefore caution should be used when prescribing Valacyclovir to women who are nursing.

Children 2 to 12 years of age are often prescribed Valacyclovir for the treatment of cold sores and chickenpox. The administration and dose for children in this age group will be determined by the healthcare professional in charge of their care. Children with recurrent genital herpes have not been studied for the effectiveness of Valacyclovir and caution should be used when this age group is being treated.

Geriatric patients exhibited a longer healing period post-treatment with Valacyclovir than age groups younger than them. Additionally, elderly patients were more likely to experience renal side effects that required reduced doses of Valacyclovir during the course of treatment. Caution is recommended with regard to this age group and treatment with Valacyclovir and a reduced dosage is recommended for safety.


Inadvertent overdose should be cautioned against as it could lead to renal complications and failure requiring hemodialysis until function is restored. A missed dose that is remembered close to the time for the next dose should be skipped.


Valacyclovir should be stored in the original container it arrived in when prescribed, retaining all dose information, instructions and warnings. Valacyclovir should be stored at room temperature away from heat, moisture, and direct sunlight. Do not store in the bathroom where steam is present and do not allow Valacyclovir to freeze. Do not keep outdated medication or medication you no longer need. Ask your health care professional to advise you on how to properly dispose of any unused or out-of=-date medication.


Valacyclovir is an antiviral drug known as a “prodrug”, which means that it is not active until introduced into the body. Once in the body, it becomes acyclovir, which works to interfere with the way the herpes virus reproduces by stopping the multiplication of the cells of the virus that invade healthy cells. While it is not a cure, it does reduce the sores exhibited with the herpes virus and allows the body to fight off the virus for itself while giving the patient ease.

Valacyclovir is prescribed for adults suffering from herpes simplex both oral and genital, herpes zoster or the shingles virus, chicken pox and cold sores. Children ages 2 to 12 are also prescribed their own size dose of Valacyclovir to treat chickenpox and cold sores, though no studies have been done on children being treated for genital herpes.

Valacyclovir should be taken at the first sign of symptoms for maximum effectiveness. Patients being treated with Valacyclovir reported relief of symptoms within 2 to 3 days and healing of sores caused by the virus within approximately one week.

Side effects are commonly mild and in the form of nausea, vomiting, and diarrhea but can also include headaches, poor appetite and loss of pleasure or low feelings. Any side effects of a nature to be believed to be related to renal function should be immediately reported to your health care physician. This includes any unusual bleeding, rashes unrelated to the virus symptoms, severe depression, and confusion or painful or diminished urination. Patients who have had bone marrow transplants, kidney transplants or any kidney disease or a family history thereof should report these conditions to their physician prior to being treated with Valacyclovir.

Store Valacyclovir at room temperature and not in the bathroom or where it could potentially be exposed to extremes of temperature or moisture. Review all supplied information prior to taking Valacyclovir. Unused or expired Valacyclovir should be disposed of under the advice of your health care professional following safe practices.


Last Reviewed:
December 23, 2017
Last Updated:
April 05, 2018
Content Source: