Generic Name: valacyclovir (val a SYE kloe veer)
Brand Names: Valtrex
What is valacyclovir?
Valacyclovir is an antiviral drug. It slows the growth and spread of the herpes virus so that the body can fight off the infection. It will not cure herpes, but it can lessen the symptoms of the infection.
Valacyclovir 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.
Valacyclovir 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.
Valacyclovir may also be used for other purposes not listed in this medication guide.
Before taking valacyclovir, 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.
Valacyclovir 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 valacyclovir.
Treatment with valacyclovir 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.
Valacyclovir will not prevent the spread of genital herpes. Herpes infections are contagious and you can infect other people even while you are taking this medicine.
Stop taking valacyclovir 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 valacyclovir 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 valacyclovir, 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. valacyclovir 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. Valacyclovir 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 this medicine to a child unless it has been prescribed by a doctor.
See also: Pregnancy and breastfeeding warnings (in more detail)
Older adults may be more likely to have harmful side effects while taking valacyclovir. Talk to your doctor about your specific risk.
How should I take valacyclovir?
Take valacyclovir 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 valacyclovir 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 valacyclovir 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.
Valacyclovir 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. Valacyclovir 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 valacyclovir tablets at room temperature away from moisture and heat. Store the liquid in a refrigerator. Do not freeze. Throw away any unused valacyclovir liquid 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?
Valacyclovir will not prevent the spread of genital herpes. Herpes infections are contagious and you can infect other people even while you are this medicine.
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.
Valacyclovir side effects
Get emergency medical help if you have any of these signs of an allergic reaction to valacyclovir: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Stop taking valacyclovir 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
Less serious valacyclovir side effects may include:
nausea, stomach pain;
headache, dizziness, tired feeling, depression;
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. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
Valacyclovir dosing information
Usual Adult Dose for Herpes Simplex Labialis:
2 g valacyclovir orally every 12 hours for a total of 2 doses (4 g)
Therapy should be started at the earliest sign of a cold sore (such as tingling, burning, or itching).
Usual Adult Dose for Herpes Simplex -- Mucocutaneous/Immunocompetent Host:
First episode: 1 g valacyclovir orally twice a day for 7 to 10 days
The efficacy has not been established if started more than 72 hours after onset of signs and symptoms.
Recurrent episode: 500 mg orally twice a day for 3 days
Therapy should be started at the first sign of a genital herpes episode. The efficacy has not been established if started more than 24 hours after onset of signs and symptoms.
Usual Adult Dose Valacyclovir for Herpes Simplex -- Suppression:
Chronic suppression of recurrent genital herpes:
Immunocompetent host: 1 g valacyclovir orally once a day
Alternative dose for immunocompetent host with a history of 9 or fewer recurrences per year: 500 mg orally once a day
Safety and efficacy beyond 1 year have not been established in immunocompetent patients.
HIV-infected host with CD4 count 100 cells/mm3 or more: 500 mg orally twice a day
Safety and efficacy beyond 6 months have not been established in HIV-infected patients.
Reduction of transmission of genital herpes in immunocompetent host with a history of 9 or fewer recurrences per year: 500 mg orally once a day for the source partner
Efficacy beyond 8 months has not been established in discordant couples.
Usual Adult Dose for Herpes Zoster:
1 g valacyclovir orally every 8 hours for 7 days
Most effective if started within 48 hours of onset of rash. The efficacy has not been established if started more than 72 hours after onset of rash.
What other drugs will affect valacyclovir?
Valacyclovir 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 valacyclovir, tell your doctor if you are also using:
lithium (Eskalith, Lithobid);
methotrexate (Rheumatrex, Trexal);
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;
medicines used to treat ulcerative colitis, such as mesalamine (Pentasa) or sulfasalazine (Azulfidine);
medicines used to prevent organ transplant rejection, such as sirolimus (Rapamune) or tacrolimus (Prograf);
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);
antiviral medicines such as adefovir (Hepsera), cidofovir (Vistide), or foscarnet (Foscavir); or
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 valacyclovir. 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.
More about valacyclovir
- Other brands: Valtrex
Related treatment guides
Where can I get more information?
- Your pharmacist can provide more information about valacyclovir.
- Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use valacyclovir only for the indication prescribed.
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