Valtrex (Valacyclovir)

(℞) Prescription Required

    Valtrex (Valacyclovir) Dosage and Side Effects

    VALTREX is an antiviral medicine. It is used to lower the ability of herpes viruses to multiply in your body

    Proper Use of this medication

    You must take VALTREX as prescribed by your doctor. If you are not sure how many caplets to take, or how often to take them, consult your doctor or pharmacist.

    You should not increase or decrease the prescribed dose or frequency unless advised by your doctor.

    For shingles, genital herpes (initial and recurrent episodes) and cold sores, for best effect, start taking your VALTREX caplets as soon as possible after your symptoms start.

    Swallow the caplets with some water. It is important to drink enough water to prevent dehydration when you are taking VALTREX. It does not matter if you take them with or without food.

    Usual adult dose:

    Shingles (herpes zoster):

    For the treatment of shingles, the usual dose of VALTREX is 1000 mg orally three times a day for 7 days. Most people take one dose when they get up in the morning, one dose mid-afternoon and one dose before they go to bed at night. Spreading the doses evenly throughout the day will help to shorten your rash and discomfort.

    Genital herpes:

    • Episodic therapy: For the treatment of an initial (first) episode of genital herpes, the usual dose of VALTREX is 1000 mg orally two times a day. The treatment is usually taken for 10 days.
    • For the treatment of recurrent episodes of genital herpes, the usual dose of VALTREX is 500 mg orally two times a day for 3 days. Take one dose in the morning and one in the evening. Take your VALTREX caplets as soon as you get the warning signs of an outbreak (i.e., itching, burning, swelling or pain in your genital area). This may actually prevent the blisters from developing.
    • Suppressive therapy: For the suppression of genital herpes, the usual dose of VALTREX is 1000 mg orally once a day. If you have a history of 9 or fewer recurrences per year, your doctor may prescribe an alternative dose of 500 mg orally once a day. You should continue to take this medicine every day and follow your doctor's instruction.
    • For the suppression of genital herpes in HIV-infected patients with CD4 cell count >100 cells/mm3, the recommended dosage of VALTREX is 500 mg orally two times a day.
    • Reduction of transmission: For the reduction of transmission of genital herpes in patients with a history of 9 or fewer recurrences per year, the usual dose of VALTREX is 500 mg once a day for the partner with the infection. Note that the efficacy of VALTREX for reducing transmission of genital herpes has not been established in individuals with multiple partners, non-heterosexual couples, and couples not counselled to use safer sex practices.

    Cold sores (herpes labialis):

    For the treatment of cold sores, the usual dose of VALTREX is 2000 mg orally two times a day for 1 day (24-hour period). The second dose should be taken around 12 hours after the first dose, but not less than 6 hours after the first dose. Do not exceed 1 day of treatment. Take your VALTREX caplets as soon as you get the warning signs of an outbreak (i.e., tingling, itching or burning).


    In case of drug overdose, contact a health care practitioner, hospital emergency department or regional Poison Control Centre immediately, even if there are no symptoms.

    Missed dose:

    If you forget to take a dose, take it as soon as you remember. Then continue with the next dose at the proper time interval. Do not double doses.

    Side Effects

    VALTREX does not often have side effects. Some people may feel sick (nausea, vomiting, diarrhea and stomach pain) or have a mild headache. These side effects are generally mild and do not usually cause patients to stop taking VALTREX.

    If you experience any of the following side effects, contact your doctor as soon as possible:

    • Skin rash (which may also occur after exposure to UV light e.g., sunbathing or using a sun bed)
    • Pain in the side (between ribs and hip) or kidney area of your back

    Tell your pharmacist or doctor if you notice any other side effects from your medicine which are not mentioned here. A complete listing of adverse events that have been reported is contained in the Product Monograph supplied to your doctor and pharmacist.

    If you feel worse or if you have taken all the caplets and do not feel better, tell your doctor as soon as possible.

    VALTREX can alter liver function tests. This is a blood test that lets your doctor know how well your liver is working. If there are any significant changes due to VALTREX, your doctor will decide on the appropriate course of action.

    Warnings and Precautions

    Before using VALTREX, tell your doctor if:

    • You have kidney problems or you are 65 years of age or older. Your doctor may give you a lower dose of VALTREX.
    • You are pregnant, planning to become pregnant, breastfeeding, or planning to breastfeed. Your doctor may decide not to prescribe VALTREX depending on your condition.

    Interactions with this medication

    Since VALTREX is a type of antiviral medication, it can inactivate a varicella or zoster vaccine before your body can develop immunity to the virus, essentially voiding the benefits of the immunization.

    Your doctor may delay giving these vaccines until VALTREX is out of your system.

    Drugs that cause kidney problems, like a non-steroidal anti-inflammatory drug (NSAID) like ibuprofen or naproxen, can interact with VALTREX.

    Since VALTREX is very similar to acyclovir (Zovirax), you should not take the two medications at the same time.

    Probenecid (Benemid) and cimetidine (Tagamet) are two drugs that may reduce you kidney’s ability to clear VALTREX out of the body, leading to high concentrations of VALTREX in the blood and possible side effects.

    This medication can make you dizzy. It’s best to avoid drinking alcohol since the combination could increase the effect.

    You should always tell your healthcare professional about all prescription, non-prescription, over-the-counter, illegal and recreational drugs, herbal remedies, nutritional and dietary supplements, and any other drugs and treatments.

    Other related products

    The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

    Back to top