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Warnings and Precautions With Valacyclovir

Warnings and precautions with valacyclovir to be aware of before starting the drug include how the medication can affect people with poor kidney function, potential drug interactions, and the possibility of the medication being passed through breast milk. Warnings and precautions with valacyclovir also extend to certain health conditions, such as immune system disorders, HIV or AIDS, and depression.

Valacyclovir: What Should I Tell My Healthcare Provider?

You should talk with your healthcare provider prior to taking valacyclovir hydrochloride (Valtrex®) 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 Warnings and Precautions With Valacyclovir

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


  • Valacyclovir 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 considering his or her kidney function. 


  • A serious condition called thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) has occurred in certain people taking valacyclovir. 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 valacyclovir (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 side effects. Therefore, your healthcare provider may give you a lower dose of valacyclovir to prevent this.
  • Valacyclovir should not be taken for more than one day when used for cold sores. Taking valacyclovir longer than this does not increase the effectiveness and may cause side effects.
  • Valacyclovir has not been studied in people with HIV who have a CD4 cell count of less than 100 cells/mm3. Also, valacyclovir has not been studied for the treatment of genital herpes in people with HIV (it has been studied for the prevention of outbreaks).
  • Valacyclovir 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).
  • Valacyclovir has not been studied in regards to preventing the spread of genital herpes in people with multiple sex partners or in non-heterosexual couples.
  • Valacyclovir should be started as soon as possible. In studies, the drug 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 valacyclovir started after three days (for shingles or genital herpes) or after a cold sore has appeared.
  • Valacyclovir 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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