Valacyclovir (Valtrex): Uses, Warnings and Key Facts

What is valacyclovir?

Valacyclovir, also spelled valaciclovir, is an antiviral medicine. The active ingredient is valacyclovir hydrochloride.

It is used for infections caused by herpes viruses. In the United States, the best-known brand name is Valtrex.

How valacyclovir works

Valacyclovir works as an antiviral. Its mechanism of action is to inhibit DNA synthesis and block viral replication.

This means it helps stop the virus from multiplying, but it does not cure the underlying viral infection.

What valacyclovir is used for

The original content lists the following therapeutic uses and indications:

• Treatment of herpes zoster and ophthalmic zoster in immunocompetent adults.
• Treatment of herpes zoster in adults with mild to moderate immunosuppression.
• Suppression and treatment of HSV infections of the skin and mucous membranes.
• Treatment of the first episode of genital herpes in immunocompetent adults and adolescents, and in immunocompromised adults.
• Treatment of genital herpes recurrences in immunocompetent adults and adolescents, and in immunocompromised adults.
• Suppression of recurrent genital herpes in immunocompromised adults and adolescents.
• Suppression and treatment of recurrent ocular infections caused by HSV in immunocompetent adults and adolescents, and in immunocompromised adults.
• Prophylaxis of CMV infection and disease after solid organ transplantation in adults and adolescents.

Posology mentioned in the original content

The following dosing information was included in the source content. Doses may vary by age, kidney function, and clinical situation, so the official leaflet and a healthcare professional should always be checked.

Contraindications

The original content lists hypersensitivity to valacyclovir or acyclovir as a contraindication.

Warnings and cautions

The source content highlights several precautions:

• Maintain adequate fluid intake in older adults and monitor them carefully.
• Use caution in renal failure and adjust the dose according to creatinine clearance.
• There is limited experience in patients with advanced cirrhosis.
• Use caution with high doses in liver disease, especially at doses of 4 g/day or more.
• No specific studies were noted in liver transplantation.
• When needed, concomitant treatment with intravenous antivirals may be considered by a clinician.
• The original content also notes a risk of adverse reactions at high doses in CMV infections.

Kidney and liver considerations

Renal insufficiency: The original content advises caution, dose adjustment according to creatinine clearance, and awareness of increased risk of neurological adverse effects.

Liver failure: The original content notes limited experience in advanced cirrhosis and caution with high doses in liver disease.

Drug interactions mentioned in the source

The original content lists the following interaction precautions:

• Nephrotoxic medicines such as aminoglycosides, organoplatin compounds, iodine contrast media, methotrexate, pentamidine, foscarnet, cyclosporine, and tacrolimus, especially if renal failure is present.
• Medicines that inhibit active renal tubular secretion.
• Cimetidine and probenecid, which may increase plasma levels.

Because interaction risk can depend on the full medicine list, a pharmacist or prescriber should review all prescription, over-the-counter, and herbal products.

Pregnancy and breastfeeding

The original content says there are limited data in pregnancy and that valacyclovir should be used only if the expected benefit outweighs the potential risk.

For breastfeeding, the source notes that acyclovir, the main metabolite of valacyclovir, is excreted in breast milk. It also states that therapeutic doses are not expected to affect newborns or breastfed infants significantly, but valacyclovir should still be used with caution during lactation and only when clinically indicated.

Possible adverse reactions

The source content lists the following side effects:

• Headache
• Nausea
• Dizziness
• Vomiting
• Diarrhea
• Rashes, including photosensitivity
• Itching

What to verify in the official leaflet

If you are reading about valacyclovir for a specific prescription or product, it is useful to confirm the following in the official FDA medication guide or package leaflet:

• The exact indication for your product
• The correct dose and duration
• Kidney-related dose adjustments
• Interaction warnings for your other medicines
• Pregnancy or breastfeeding guidance

Frequently asked questions

Safety reminder

Before using valacyclovir, make sure a healthcare professional has reviewed your symptoms, kidney function, liver history, pregnancy or breastfeeding status, and all other medicines you take. If you have urgent or severe symptoms, seek medical care promptly.

Sources and reference links

The original content cites FDA and U.S. pharmacopoeia-based resources. Helpful reference links include the FDA medication guide and ingredient databases listed below.