How does this medication work? What will it do for me?
Valacyclovir belongs to the class of medications known as antivirals. It is used to treat a viral infection affecting the skin known as shingles (herpes zoster). It is also used to treat cold sores, and to treat and prevent recurrences of genital herpes. It works by interfering with the way the virus reproduces. Valacyclovir works by stopping the virus from multiplying and spreading to nearby healthy cells.
It does not cure shingles, cold sores, or genital herpes, but it does help the sores to heal more quickly, and it relieves pain and discomfort. When used to prevent recurrences of herpes, it also reduces the risk of transmission (spreading) of the infection to others.
This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.
Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.
Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.
What form(s) does this medication come in?
Each blue, oval, biconvex, film-coated caplet with "M191" imprinted with white ink on one side and plain on the other side, contains valacyclovir 500 mg (as valacyclovir hydrochloride). Nonmedicinal ingredients: magnesium stearate, microcrystalline cellulose, FD&C Blue No. 2/ Indigo Carmine Aluminum Lake, hydroxypropyl methylcellulose, polyethylene glycol, n-butyl alcohol, shellac glaze, simethicone emulsion, soy lecithin, and titanium dioxide.
Each white, oval, biconvex, film-coated caplet with "m192" imprinted with black ink on one side and plain on the other side, contains valacyclovir 1,000 mg (as valacyclovir hydrochloride). Nonmedicinal ingredients: magnesium stearate, microcrystalline cellulose, hydroxypropyl methylcellulose, polyethylene glycol, titanium dioxide, industrial methylated spirit, iron oxide black, isopropyl alcohol, n-butyl alcohol, propylene glycol, and shellac glaze.
How should I use this medication?
The recommended adult dose of valacyclovir to treat shingles is 1,000 mg 3 times daily for 7 days. The treatment should be started within 72 hours of the onset of the rash.
To treat the first episode of genital herpes, the dose of valacyclovir is 1,000 mg twice daily for 10 days. Treatment should be started within 72 hours of the onset of symptoms, and ideally within 48 hours for best effectiveness.
To treat recurrent genital herpes, the dose of valacyclovir is 500 mg twice daily for 3 days. The treatment should be started at the first sign or symptom of recurrence.
To prevent recurrences of genital herpes, the recommended dose is 1,000 mg once daily. For people with a history of 9 or fewer recurrences per year, the recommended dosage of valacyclovir is 500 mg orally once daily. This dose helps to reduce the risk of transmitting genital herpes to others.
To treat cold sores, the usual dose of valacyclovir is 2,000 mg at the first sign of symptoms, followed by another 2,000 mg 12 hours later. The treatment should be started at the first sign of a cold sore (tingling, itching, or burning sensations) for best effectiveness.
People with poor kidney function may need lower doses.
Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way you are using the medication without talking to your doctor.
Valacyclovir can be taken with or without food. If it causes stomach upset, taking it with food may help. Make sure you drink enough water to prevent dehydration while taking valacyclovir.
It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular dosing schedule. If it is almost time for your next dose, skip the missed dose and continue with your usual dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.
Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.
Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.
Who should NOT take this medication?
Do not take this medication if you are allergic to valacyclovir, acyclovir, or any ingredients of the medication.
What side effects are possible with this medication?
Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.
The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.
The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.
Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.
- abdominal pain
- increased sensitivity to UV light
- skin rash
Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.
Check with your doctor as soon as possible if any of the following side effects occur:
- behaviour changes
- pain in the side between the ribs and hip or kidney area of the back
- signs of anemia caused by red blood cell destruction (e.g., abdominal pain, bloody diarrhea, fatigue, nausea, vomiting, confusion, swelling of hands and feet)
- signs of bleeding (e.g., unusual bruising or bleeding, bleeding gums, unexplained nosebleeds)
- signs of decreased kidney function (e.g., decreased urine production, loss of appetite, nausea)
Stop taking the medication and seek immediate medical attention if any of the following occur:
- signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, swelling of the face and throat)
- signs of a severe skin reaction (e.g., a rash combined with fever or discomfort, a rash covering a large area of the body, a rash that spreads quickly, blistering, peeling)
Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.
Are there any other precautions or warnings for this medication?
Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.
Genital herpes: To reduce the risk of spreading the virus, wash your hands immediately after touching your skin sores. You should avoid intimate contact when live lesions are visible on your skin. The herpes virus can still be spread even when you do not have blisters or sores.
Immunosuppression (weak immune system): People who have a weakened immune system should only use valacyclovir if the benefits outweigh the risks. If you have had an organ transplant, are infected with HIV, or otherwise have a weak immune system, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Kidney disease: Valacyclovir may cause decreased kidney function or kidney failure. People with kidney disease may need a lower dose of this medication. If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
If you experience signs of decreased kidney function, such as decreased urine production, nausea, fatigue, or muscle twitches or cramps, contact your doctor as soon as possible.
Safer sex: Valacyclovir, when taken in appropriate doses each day, can reduce the risk of passing genital herpes to sexual partners. It should be used in combination with safer sex practices such as using condoms and dental dams. If you have any questions about practicing safer sex, speak to your doctor.
Systemic infection: The safety and effectiveness of using valacyclovir to treat herpes zoster infection that is inside the body has not been established. This is not an accepted use for this medication.
Pregnancy: Although valacyclovir does not appear to increase the risk of harm to an unborn baby, the safety of valacyclovir use during pregnancy has not been established. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.
Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking valacyclovir, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.
Children: The safety and effectiveness of using this medication have not been established for children.
Seniors: Seniors are more likely to have decreased kidney function than younger adults. A decreased dose of valacyclovir may be required. It is important for seniors to drink enough water while taking this medication, to stay well-hydrated.
What other drugs could interact with this medication?
There may be an interaction between valacyclovir and any of the following:
- theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
- varicella virus vaccine
- zoster vaccine
If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:
- stop taking one of the medications,
- change one of the medications to another,
- change how you are taking one or both of the medications, or
- leave everything as is.
An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.
Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.
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