Valtrex Side Effects

Valtrex is an antiviral drug. It slows the growth and spread of the herpes virus so that the body can fight off the infection. Valtrex will not cure herpes, but it can lessen the symptoms of the infection.

Valtrex is used to treat infections caused by herpes viruses in adults and children. Illnesses caused by herpes viruses include genital herpes, cold sores, shingles, and chickenpox.

Valtrex is used to treat cold sores in children who are at least 12 years old, and to treat chickenpox in children who are at least 2 years old.

Do not take this medicine if you are allergic to valacyclovir or acyclovir (Zovirax).

If you have certain conditions, you may need a dose adjustment or special tests to safely take this medication. Before taking Valtrex, tell your doctor if you have:

  • HIV/AIDS, or other conditions that can weaken the immune system;
  • kidney disease (or if you are on dialysis); or
  • if you have had a kidney or bone marrow transplant.

FDA pregnancy category B. This medication is not expected to be harmful to an unborn baby. However, herpes virus can be passed from an infected mother to her baby during childbirth. If you have genital herpes, it is very important to prevent herpes lesions during your pregnancy so that you do not have a genital lesion when your baby is born. Valtrex passes into breast milk and may harm a nursing infant. Do not take this medication without telling your doctor if you are breast-feeding a baby. Do not give Valtrex to a child unless it has been prescribed by a doctor. Older adults may be more likely to have harmful side effects while taking Valtrex. Talk to your doctor about your specific risk.

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop taking Valtrex and call your doctor right away if you have any of the following signs of a serious side effect that can harm red blood cells:

  • fever, easy bruising or bleeding;
  • red spots on the skin (not related to herpes or chickenpox);
  • bloody diarrhea, vomiting;
  • pale or yellowed skin;
  • weakness or fainting; or
  • urinating less than usual or not at all.

Call your doctor at once if you have any of these other serious side effects:

  • pain in your lower back;
  • drowsiness, mood changes, increased thirst, loss of appetite, nausea and vomiting;
  • swelling, weight gain, feeling short of breath;
  • confusion, agitation, aggression, hallucinations, trouble concentrating;
  • feeling shaky or unsteady;
  • problems with speech or vision; or
  • seizure (convulsions).

Less serious Valtrex side effects may include:

  • nausea, stomach pain;
  • headache, dizziness, tired feeling, depression;
  • joint pain;
  • menstrual pain;
  • mild skin rash; or
  • stuffy nose, sore throat.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.

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