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Valtrex Precautions and Warnings

Valtrex precautions and warnings include potential drug interactions, possible risks for people with poor kidney function, and whether women who are nursing should take it. Before taking Valtrex, talk to your healthcare provider about any health conditions you may have, such as kidney disease, AIDS, or depression. Valtrex precautions and warnings also extend to any medications you are taking, including prescription and non-prescription medications, vitamins, and herbal supplements.

Valtrex: What Should I Tell My Healthcare Provider?

You should talk with your healthcare provider prior to taking Valtrex® (valacyclovir hydrochloride) if you have:
  • Kidney disease or kidney failure
  • Had a bone marrow or kidney transplant
  • HIV or AIDS
  • Depression
  • Problems with the immune system or immune system disorders, such as cancer
  • Any allergies, including allergies to foods, dyes, or preservatives.
Also, let your healthcare provider know if you are:
  • Pregnant or thinking of becoming pregnant
  • Breastfeeding.
It's also important to tell your healthcare provider about all the medicines you are taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.

Specific Valtrex Warnings and Precautions

Valtrex warnings and precautions to be aware of include the following:
  • Valtrex can interact with certain medications (see Valtrex Drug Interactions).
  • Valtrex is considered a pregnancy Category B medication. This means that Valtrex is probably safe for use during pregnancy. However, because Valtrex has not been studied in pregnant women, the full risks of using it during pregnancy are not known. Women who are pregnant should take Valtrex only if the benefits outweigh the risks to the developing baby. Discuss possible risks and benefits with your healthcare provider before using Valtrex when pregnant (see Valtrex During Pregnancy).
  • Valtrex is passed through breast milk. Therefore, if you are breastfeeding, or plan to start breastfeeding, be sure to talk with your healthcare provider about this. He or she can decide whether taking Valtrex while nursing is okay for your particular situation.
  • The dose of Valtrex must be reduced in people with poor kidney function. If normal doses of Valtrex are used in people with kidney problems, kidney failure and other serious problems may occur. Your dose of Valtrex may also need to be reduced if you are taking other medications that can harm the kidneys.


  • Valtrex can cause central nervous system side effects, such as confusion, hallucinations, delirium, or seizures, especially if a person is given too high of a dosage with respect to his or her kidney function. 


  • A serious condition called thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) has occurred in certain people taking Valtrex. TTP/HUS is a condition involving very low red blood cell and platelet counts. In TTP/HUS, the body forms many small blood clots. This dangerous condition has occurred in people with HIV and people who have had a stem cell transplant or kidney transplant. These people were taking unusually high doses of Valtrex (8 grams per day). Talk to your healthcare provider right away if you have signs of TTP/HUS, including unusual bruising and bleeding or unexplained fever.
  • People 65 years of age and older have a higher chance of certain Valtrex side effects. Therefore, your healthcare provider may give you a lower dose of Valtrex.
  • Valtrex should not be taken for more than one day when used for cold sores. Taking Valtrex longer than this does not increase the effectiveness and may cause side effects.
  • Valtrex has not been studied in people with HIV who have a CD4 cell count less than 100 cells/mm3. Also, Valtrex has not been studied for the treatment of genital herpes in people with HIV (it has been studied for the prevention of outbreaks).
  • Valtrex has not been studied in people with poorly functioning immune systems (other than people with HIV). This may include people with cancer and people taking immune-suppressing medications (such as after a transplant).
  • Valtrex has not been studied in preventing the spread of genital herpes in people with multiple sex partners or in non-heterosexual couples.
  • Valtrex should be started as soon as possible. In studies, Valtrex was always started within three days of symptoms (for shingles or genital herpes) or before a cold sore was visible. There is no information available about the effectiveness of Valtrex started after three days (for shingles or genital herpes) or after a cold sore has appeared.
  • Valtrex will not cure genital herpes. You should avoid sexual contact while having an outbreak (or if you think you are about to have an outbreak). You should always use condoms, as genital herpes can be spread at any time.
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