Valtrex (valacyclovir) vs. Valcyte (valganciclovir): What's the difference?

What is Valtrex? What is Valcyte?

Valtrex (valacyclovir) is a nucleoside analog antiviral drug used to treat shingles (herpes zoster) and genital herpes (herpes simplex genitalis) infections, and cold sores (herpes labialis). Valtrex mimics a building block of DNA and stops the spread of herpes virus in the body by preventing the viral DNA replication necessary for viruses to multiply. Other nucleoside analogs include acyclovir (Zovirax) and famciclovir (Famvir). Valacyclovir is actually a "prodrug," that is not active itself but rather, it is converted to acyclovir in the body, and it is acyclovir that is active against the viruses. (Acyclovir is available as a topical, oral, and intravenous medication.) Valtrex is therefore active against the same viruses as acyclovir, but it has a longer duration of action than acyclovir and may be taken fewer times per day.

Valcyte (valganciclovir) is an antiviral drug used to prevent disease caused by a virus called cytomegalovirus (CMV) in people who have received organ transplants and cancer chemotherapy treatment. CMV disease can lead to serious infections in the body, including an infection in the eye (CMV retinitis) that can cause blindness. Valcyte works by slowing the growth of the CMV virus and helping prevent the spread of infection to other areas of the body. Valcyte is also used to treat CMV retinitis in people with AIDS. Valcyte helps control CMV retinitis and decrease the risk of blindness. Valcyte is not a cure for CMV disease.

What are the side effects of Valtrex and Valcyte?

Valtrex

The side effect profile of Valtrex is similar to that of acyclovir (Zovirax).

Common side effects are:

Other important side effects are:

More serious side effects include central nervous system side effects which are more likely to happen in the elderly, for example:

Valcyte

Valcyte can cause serious side effects, including:

  • Blood and bone marrow problems. Valcyte can affect the bone marrow, lowering the amount of your white blood cells, red blood cells, and platelets, and may cause serious and life-threatening problems.
  • Kidney failure. Kidney failure may occur in people who are elderly, people who take Valcyte with certain other medicines, or people who are not adequately hydrated.
  • Fertility problems. Valcyte may lower sperm count in males and cause fertility problems. Valcyte may also cause fertility problems in women. Talk to your doctor if this is a concern for you.
  • Birth defects. Valcyte causes birth defects in animals. It is not known if Valcyte causes birth defects in people. If you are a female who can become pregnant, use effective birth control during treatment with Valcyte and for at least 30 days after treatment. If you are pregnant, talk to your doctor before starting treatment with Valcyte. If you are a female who can become pregnant, have a pregnancy test done before starting Valcyte.
    • Tell your doctor right away if you become pregnant during treatment with Valcyte.
    • Males should use condoms during treatment with Valcyte, and for at least 90 days after treatment, if their female sexual partner can become pregnant. Talk to your doctor if you have questions about birth control.
  • Cancer. Valcyte causes cancer in animals and may potentially cause cancer in people.

Your doctor will do regular blood tests during treatment with Valcyte to check you for side effects. Your doctor may change your dose or stop treatment with Valcyte if you have serious side effects.

Common side effects

The most common side effects of Valcyte in adults include:

The most common side effects of Valcyte in children include:

These are not all the possible side effects of Valcyte. Call your doctor for medical advice about side effects.

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What is the dosage of Valtrex vs. Valcyte?

Valtrex

  • Valtrex may be taken with or without food.
  • In people with kidney disease, doses need to be reduced.
  • For the treatment of herpes zoster (shingles), the usual dose is 1 gram 3 times a day for 7 days. Treatment should begin at the first symptom and is most effective if started within 48 hours of the onset of rash.
  • The dose for chickenpox is 20 mg/kg 3 times daily for 5 days (maximum dose is 1000 mg 3 times daily) and treatment should start at the earliest sign or symptom.
  • For the treatment of an initial episode of genital herpes, the usual dose is 1 gram (1000 mg) twice daily for 10 days. For the treatment of recurrent genital herpes, the usual dose is 500 mg twice daily for 3 days. For best results, treatment should be initiated within 12 hours of the start of symptoms.
  • The dose for cold sores is 2000 mg (2 grams) every 12 hours for 1 day.

Valcyte

  • Take Valcyte exactly as your doctor tells you. Your dose of Valcyte will depend on your medical condition.
  • Adults should only take Valcyte tablets. Children may take either Valcyte tablets or oral solution.
  • Take Valcyte with food.
  • Do not break or crush Valcyte tablets. Avoid contact with your skin or eyes. If you come in contact with the contents of the tablet or oral solution, wash your skin well with soap and water or rinse your eyes well with plain water.
  • If your child is prescribed Valcyte for oral solution, your pharmacist will give you oral dosing dispensers to measure your child’s dose of Valcyte for oral solution. To be sure you receive the prescribed dose, it is important to use the dispenser provided to you. Ask your pharmacist if you have any questions. If you lose or damage your oral dispensers and cannot use them, contact your pharmacist.
  • If you take too much Valcyte, call your doctor or go to the nearest hospital emergency room right away.

What drugs interact with Valtrex and Valcyte?

Valtrex

Probenecid (Benemid) and cimetidine (Tagamet) may reduce the kidney's clearance of Valtrex, leading to higher concentrations in the blood. This may lead to side effects of Valtrex.

Valcyte

Valcyte can harm your kidneys. This effect is increased when you also use certain other medicines, including:

Other drugs may interact with Valcyte, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using. Valcyte and other medicines may affect each other and cause serious side effects. Keep a list of your medicines to show your doctor and pharmacist. Ask your doctor or pharmacist for a list of medicines that interact with Valcyte. Do not start taking a new medicine without telling your doctor. Your doctor can tell you if it is safe to take Valcyte with other medicines.

Are Valtrex and Valcyte safe to use while pregnant or breastfeeding?

Valtrex

Valtrex showed no effects on the fetus in animal studies; however, there has been no adequate evaluation of valacyclovir (or acyclovir) in pregnant women. The incidence of birth defects in women taking acyclovir is about the same as in the general population. Valtrex should only be used during pregnancy when the benefits to the mother outweigh risks to the fetus.

It is not known whether Valtrex is excreted into breast milk. It is known, however, that among women taking acyclovir, concentrations of acyclovir in breast milk are about four times higher than in the mother's blood. The safety of valacyclovir in breastfeeding infants has not been established. Methods other than breastfeeding should be considered if valacyclovir must be taken while nursing.

Valcyte

Valcyte causes birth defects in animals. It is not known if Valcyte causes birth defects in people. If you are a female who can become pregnant, use effective birth control during treatment with Valcyte and for at least 30 days after treatment. If you are pregnant, talk to your doctor before starting treatment with Valcyte. If you are a female who can become pregnant, have a pregnancy test done before starting Valcyte. Tell your doctor right away if you become pregnant during treatment with Valcyte. Males should use condoms during treatment with Valcyte, and for at least 90 days after treatment, if their female sexual partner can become pregnant. Talk to your doctor if you have questions about birth control.

Do not breastfeed if you take Valcyte. Do not breastfeed if you have human immunodeficiency virus (HIV) because of the risk of passing HIV to your baby. Talk to your doctor about the best way to feed your baby.

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Summary

Valtrex (valacyclovir) and Valcyte (valganciclovir) are antiviral drugs used to treat different conditions. Valtrex is used to treat shingles (herpes zoster), genital herpes (herpes simplex genitalis), and cold sores (herpes labialis). Valcyte is used to prevent disease caused by cytomegalovirus (CMV) in people who have received organ transplants and cancer chemotherapy treatment and to treat CMV retinitis in people with AIDS.

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Medically Reviewed on 9/30/2019
References
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