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.
Valtrex may also be used for other purposes not listed in this medication guide.
Important information
Before taking Valtrex, tell your doctor if you have HIV/AIDS, a weak immune system, kidney disease (or if you are on dialysis), or if you have had a kidney or bone marrow transplant.
Valtrex can be harmful to the kidneys, and these effects are increased when it is used together with other medicines that can harm the kidneys. Tell your doctor about all other medications you are using. You may need dose adjustments or special tests when taking certain medications together with Valtrex.
Treatment with Valtrex should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).
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 will not prevent the spread of genital herpes. Herpes infections are contagious and you can infect other people even while you are taking with Valtrex.
Stop taking Valtrex and call your doctor right away if you have any signs of a serious side effect that can harm red blood cells, such as: fever, easy bruising or bleeding, red spots on the skin (not related to herpes or chickenpox), bloody diarrhea, vomiting, pale or yellowed skin, weakness, fainting, or urinating less than usual or not at all.
Do not give Valtrex to a child unless it has been prescribed by a doctor.
Before taking this medicine
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:
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HIV/AIDS, or other conditions that can weaken the immune system;
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kidney disease (or if you are on dialysis); or
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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.
How should I take Valtrex?
Take Valtrex exactly as it was prescribed for you. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor. Follow the directions on your prescription label.
Treatment with Valtrex should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters). This medication might not be as effective if you first start taking it 1 or 2 days after the start of your symptoms.
Take each dose with a full glass of water. Drink plenty of water while you are taking Valtrex to keep your kidneys working properly. Shake the oral suspension (liquid) well just before you measure a dose. To be sure you get the correct dose, measure the liquid with a marked measuring spoon or medicine cup, not with a regular table spoon. If you do not have a dose-measuring device, ask your pharmacist for one.
Valtrex can be taken with or without food.
Take this medication for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated. Valtrex will not treat a viral infection such as the common cold or flu.
Lesions caused by herpes viruses should be kept as clean and dry as possible. Wearing loose clothing may help to prevent irritation of the lesions.
Store Valtrex tablets at room temperature away from moisture and heat. Store Valtrex liquid in a refrigerator. Do not freeze. Throw away any unused Valtrex that is older than 28 days.
What happens if I miss a dose?
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at the next regularly scheduled time. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention if you think you have used too much of this medicine.
Overdose symptoms may include urinating less than usual or not at all.
What should I avoid?
Valtrex will not prevent the spread of genital herpes. Herpes infections are contagious and you can infect other people even while you are taking with Valtrex.
Avoid sexual intercourse or use a latex condom to prevent spreading the virus to others. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.
Valtrex side effects
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:
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fever, easy bruising or bleeding;
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red spots on the skin (not related to herpes or chickenpox);
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bloody diarrhea, vomiting;
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pale or yellowed skin;
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weakness or fainting; or
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urinating less than usual or not at all.
Call your doctor at once if you have any of these other serious side effects:
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pain in your lower back;
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drowsiness, mood changes, increased thirst, loss of appetite, nausea and vomiting;
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swelling, weight gain, feeling short of breath;
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confusion, agitation, aggression, hallucinations, trouble concentrating;
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feeling shaky or unsteady;
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problems with speech or vision; or
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seizure (convulsions).
Less serious Valtrex side effects may include:
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nausea, stomach pain;
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headache, dizziness, tired feeling, depression;
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joint pain;
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menstrual pain;
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mild skin rash; or
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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. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
What other drugs will affect Valtrex?
Valtrex can be harmful to the kidneys, and these effects are increased when it is used together with other medicines that can harm the kidneys. Before taking Valtrex, tell your doctor if you are also using:
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lithium (Eskalith, Lithobid);
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methotrexate (Rheumatrex, Trexal);
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pain or arthritis medicines such as aspirin (Anacin, Excedrin), acetaminophen (Tylenol), diclofenac (Voltaren), etodolac (Lodine), ibuprofen (Advil, Motrin), indomethacin (Indocin), naproxen (Aleve, Naprosyn), and others;
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medicines used to treat ulcerative colitis, such as mesalamine (Pentasa) or sulfasalazine (Azulfidine);
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medicines used to prevent organ transplant rejection, such as sirolimus (Rapamune) or tacrolimus (Prograf);
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IV antibiotics such as amphotericin B (Fungizone, AmBisome, Amphotec, Abelcet), amikacin (Amikin), bacitracin (Baci-IM), capreomycin (Capastat), gentamicin (Garamycin), kanamycin (Kantrex), streptomycin, or vancomycin (Vancocin, Vancoled);
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antiviral medicines such as adefovir (Hepsera), cidofovir (Vistide), or foscarnet (Foscavir); or
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cancer medicine such as aldesleukin (Proleukin), carmustine (BiCNU, Gliadel), cisplatin (Platinol), ifosfamide (Ifex), oxaliplatin (Eloxatin), plicamycin (Mithracin), streptozocin (Zanosar), or tretinoin (Vesanoid).
This list is not complete and there may be other drugs that can interact with Valtrex. Tell your doctor about all your prescription and over-the-counter medications, vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start a new medication without telling your doctor.
