Valacyclovir

What Is Valacyclovir?

Valacyclovir is a prescription antiviral medicine. It belongs to a group called nucleoside analog antivirals (also called guanine analogs). It is a “prodrug,” which means the body changes it into its active form, acyclovir, after it is swallowed. This allows more of the medicine to be absorbed than with acyclovir taken by mouth. It is sold under the brand name Valtrex in the United States and as generic versions. It is used to treat and prevent infections caused by certain herpes viruses.

FDA-Approved Uses

In adults:

• Cold sores (herpes labialis), caused by herpes simplex virus (HSV)
• Genital herpes, including treatment of the first outbreak, treatment of recurrent outbreaks, daily suppressive therapy to reduce outbreaks, and reduction of the risk of passing genital herpes to a partner (in people with a single partner, together with safer sex practices)
• Herpes zoster (shingles), caused by the varicella-zoster virus
• Suppression of recurrent genital herpes in people with HIV who have a healthy immune system

In children:

• Cold sores in children 12 years of age and older
• Chickenpox in children 2 to under 18 years of age

Other Prescribed Uses

Specialists sometimes prescribe valacyclovir for other herpes-related conditions, such as herpes infections of the eye or in people with weakened immune systems, or to help prevent certain infections after transplant. These decisions belong to the treating specialist.

Available Forms and Strengths

• Tablets (caplets): Valacyclovir 500mg, Valacyclovir 1g
• Oral suspension: made by the pharmacy from tablets in some cases, for people who cannot swallow tablets

Available forms and strengths can vary by manufacturer and country.

What Is the Recommended Dosage of Valacyclovir?

There is no single dose that fits everyone. The prescribed dose and length of treatment depend on several factors:

• The condition being treated. Cold sores may be treated with a short, one-day course. Shingles and first genital herpes outbreaks are usually treated for several days. Suppressive therapy may be taken daily for months or longer.
• Age. Children are dosed differently from adults.
• Body weight (in children).
• Kidney function. Valacyclovir leaves the body through the kidneys, so people with reduced kidney function often need lower or less frequent doses.
• Immune status. People with weakened immune systems may need a different plan under specialist direction.
• Timing. Treatment works best when started early, ideally at the first sign of symptoms such as tingling, burning, or itching.

Valacyclovir can be taken with or without food. Drinking plenty of water while taking it is advised, especially for older adults and people with kidney concerns.

Take valacyclovir exactly as your licensed medical specialist or pharmacist instructs. Do not change the dose, stop early, or extend treatment on your own, even if symptoms improve.

How Valacyclovir Works

After it is swallowed, valacyclovir is quickly changed in the body into acyclovir. Inside cells infected by the herpes virus, acyclovir is changed into an active form that looks similar to one of the building blocks of viral DNA. The virus mistakenly uses it when copying its genetic material. This blocks the enzyme the virus needs to make more DNA, so the virus cannot multiply well.

Valacyclovir treats and controls herpes virus infections by slowing viral growth. It can shorten outbreaks and reduce symptoms, and daily use can lower how often outbreaks occur. It does not cure herpes. The virus stays in the body in an inactive form and can become active again. Valacyclovir does not work against bacterial or fungal infections, and it is not used for the common cold or flu.

Is a Prescription Required to Buy Valacyclovir Online?

In the United States, valacyclovir is a prescription-only medicine. A licensed healthcare professional must evaluate you before it is prescribed.

Depending on the condition, the specialist may be:

• A primary care physician
• A dermatologist (for cold sores and skin-related herpes infections)
• A gynecologist or urologist (for genital herpes)
• An infectious disease specialist (for frequent, severe, or complicated infections, or in people with weakened immune systems)
• A pediatrician (for children)
• An ophthalmologist (for herpes infections of the eye)

Only buy valacyclovir from a licensed pharmacy that requires a valid prescription. Be careful with websites that sell it without one or that ship medicines from overseas without verification. Counterfeit, expired, or improperly stored products can be unsafe. Products labeled for animals are not approved for people and should never be used.

Side Effects of Valacyclovir

Most people tolerate valacyclovir well, but side effects can occur.

Common Side Effects

• Headache
• Nausea
• Stomach pain
• Vomiting or diarrhea
• Dizziness
• Tiredness
• Rash
• Joint pain (in some patients)

These are often mild. Talk to your pharmacist or doctor if they bother you or do not go away.

Serious Side Effects

Serious reactions are uncommon but possible. Get medical help right away if you notice:

• Swelling of the face, lips, tongue, or throat, or trouble breathing (allergic reaction)
• Severe skin reactions, such as blistering, peeling, or sores in the mouth
• Confusion, hallucinations, agitation, severe drowsiness, tremor, or seizures (more likely in older adults and people with kidney problems)
• Decreased urination, new swelling, or unusual tiredness (possible kidney problems)
• Unusual bruising or bleeding, pale skin, fever, or extreme tiredness (possible blood problems)
• Severe or lasting stomach pain or diarrhea

Call emergency services if you have trouble breathing or think you are having a life-threatening reaction.

Drug Interactions

Valacyclovir has relatively few major interactions, but caution is needed with medicines that affect the kidneys. Major categories include:

• Medicines that can harm the kidneys, such as certain antibiotics, amphotericin B, cyclosporine, tacrolimus, and NSAIDs (such as ibuprofen or naproxen), especially at high doses or with dehydration
• Probenecid and cimetidine, which can raise acyclovir levels
• Mycophenolate mofetil, an immune-suppressing medicine, whose levels and those of acyclovir may both rise
• Other medicines cleared by the kidneys, which may need dose review, especially in older adults
• Theophylline, whose levels may increase
• Live vaccines. The chickenpox and shingles live vaccines may be affected by antiviral medicines. Ask your provider about timing.

Tell your provider about all over-the-counter medicines (including NSAIDs), vitamins, supplements, and herbal products. Also mention alcohol use.

Give your licensed medical specialist and pharmacist a complete, up-to-date list of everything you take. This list is not complete, so always check before starting or stopping any medicine.

Safety & Important Considerations

• Kidney disease: Dose changes are required for reduced kidney function. Kidney problems and nervous system side effects are more likely when the dose is too high for a person’s kidney function.
• Hydration: Drink plenty of fluids during treatment, especially with high doses or in older adults.
• TTP/HUS warning: A rare and serious blood and kidney condition (thrombotic thrombocytopenic purpura/hemolytic uremic syndrome) has been reported in people with advanced HIV and in transplant recipients receiving high doses. Report unusual bruising, tiredness, or reduced urination promptly.
• Nervous system effects: Confusion, hallucinations, and seizures can occur, particularly in older adults and people with kidney impairment.
• Weakened immune systems: Treatment plans may differ, and a specialist should guide therapy.
• Genital herpes: Valacyclovir lowers but does not eliminate the chance of passing herpes to a partner. Use safer sex practices, avoid sexual contact during outbreaks or when symptoms begin, and follow your provider’s advice.
• Pregnancy: Available data have not shown a clear increase in birth defects, but information is limited. Herpes infection itself can affect pregnancy, so treatment decisions are made by weighing benefits and risks. Tell your provider if you are pregnant, may become pregnant, or are trying to conceive.
• Breastfeeding: Acyclovir, the active form, passes into breast milk. Discuss the risks and benefits with your provider.
• Children: Valacyclovir is used in children for certain conditions, with dosing determined by a specialist. Safety and effectiveness have not been established for all uses or ages.
• Older adults: Kidney function often declines with age, so dose adjustment may be needed. Older adults are more likely to have confusion or dizziness and often take multiple medicines, which raises the chance of interactions.
• Driving and machinery: Dizziness or confusion can occur. Use caution until you know how the medicine affects you.

Who This Medication Is For

Valacyclovir is prescribed for adults and, for certain conditions, children who have herpes simplex virus infections (cold sores or genital herpes), shingles, or chickenpox, within its approved indications. It is also used to reduce outbreaks in people with frequent recurrences. Whether it is appropriate depends on the type of infection, immune status, kidney function, medical history, and other medicines.

Who Should Not Take Valacyclovir

Valacyclovir is not suitable for everyone. Do not take it if:

• You have had an allergic reaction to valacyclovir, acyclovir, or any ingredient in the product.

Use extra caution and discuss risks with your provider if you have:

• Kidney disease or dehydration
• Advanced HIV disease or a weakened immune system
• A history of a bone marrow or kidney transplant
• Liver disease
• Age of 65 years or older
• Pregnancy, plans for pregnancy, or breastfeeding
• A history of seizures or nervous system problems

What to Do If You Miss a Dose

• Take the missed dose as soon as you remember.
• If it is almost time for your next dose, skip the missed one and go back to your regular schedule.
• Do not take two doses at once to make up for a missed dose.
• If you are unsure what to do, or you are taking a short or single-day regimen, contact your licensed medical specialist or pharmacist. Missed doses can affect how well the infection is treated.

Related medications to Valacyclovir

Other medicines exist for herpes virus infections, and the right one depends on the type of infection and the person’s health. Only a licensed specialist can decide whether a different medicine is appropriate.

Other antivirals in the same class:

• Acyclovir, the active form of valacyclovir, available as tablets, liquid, cream or ointment, and IV
• Famciclovir, taken by mouth for cold sores, genital herpes, and shingles
• Ganciclovir and valganciclovir, used mainly for cytomegalovirus (CMV) rather than herpes simplex or shingles

Other options:

• Penciclovir cream and docosanol cream for cold sores
• Foscarnet or cidofovir, given by IV, sometimes used for herpes viruses that are resistant to acyclovir
• Pain relief and supportive care measures, chosen by your provider
• Shingles vaccine, which helps prevent shingles but is not a treatment for an active outbreak

Do not switch or stop valacyclovir without talking to your licensed medical specialist.

Storage Instructions

• Tablets: Store at room temperature, generally between 59°F and 77°F (15°C and 25°C), in the original container. Keep them dry and protected from moisture and light. Avoid storing them in a bathroom.
• Pharmacy-prepared liquid (if prescribed): Follow the pharmacy label for storage and for how long to keep it. It is often kept in a refrigerator and discarded after a set number of days. Shake well before each use if directed.
• Child safety: Keep all medicines out of reach and sight of children and pets, preferably in a locked or high cabinet.
• Do not use medicine past its expiration date. Ask your pharmacist about safe disposal of unused or expired medicine.

Disclaimer:

This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Patients must consult a licensed medical specialist, such as a primary care physician, dermatologist, gynecologist, infectious disease specialist, or ophthalmologist, depending on the condition, before starting, changing, or stopping treatment. Treatment decisions must be based on a full clinical evaluation by a qualified specialist. Information about dosing, strengths, and safety may change, so always follow the guidance of your prescriber and the current product labeling.