Generic Valtrex (Valacyclovir): Uses, dosage, side effects, warnings & patient reviews

What is Valtrex (Valacyclovir)?

Valtrex (valacyclovir) is an oral antiviral prescription medication. It is classified as a prodrug, meaning it is converted into its active form, acyclovir, inside the human body. This conversion allows valacyclovir to be absorbed much more efficiently from the digestive tract than acyclovir itself.

The key patient benefit is a significantly more convenient dosing schedule. While acyclovir typically requires dosing multiple times per day, Valtrex is usually taken only once or twice daily for most conditions, improving adherence to treatment.

How Valtrex Works

Once converted to acyclovir in the body, the drug works by inhibiting the replication of herpes viruses. It is incorporated into the viral DNA chain, causing premature chain termination and preventing the virus from multiplying. This action helps control outbreaks, reduces healing time, and can decrease the frequency of future episodes.

Valtrex is effective against several types of herpes viruses, including herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), and varicella-zoster virus (VZV).

How to Take Valtrex

Following the correct administration instructions is essential for Valtrex’s effectiveness and to minimize the risk of side effects, particularly those affecting the kidneys.

Administration and Hydration

Swallow the tablet whole with a full glass of water. Valtrex can be taken with or without food.

Maintaining adequate hydration is crucial. Drink plenty of water or fluids while you are taking this medicine. This helps prevent the rare but serious side effect of the drug forming crystals in your kidneys, which is more likely if you are dehydrated. Patients with pre-existing kidney disease require dosage adjustment and careful monitoring.

Initiating Treatment

For the best results, treatment should be started at the earliest sign or symptom of an outbreak (e.g., tingling, itching, burning, or the appearance of a blister). Starting medication after lesions have already formed may be less effective.

Course Completion

Finish the entire prescribed course of medication, even if symptoms improve after a few days, unless directed otherwise by your doctor. For suppressive therapy (daily dosing to prevent outbreaks), take the medication exactly as prescribed, usually once daily.

Missed Dose

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and take your next dose at the regular time. Do not take two doses to make up for a missed one.

Side Effects of Valtrex

Most people tolerate Valtrex well. Side effects are generally mild. It can be helpful to understand the range of possible reactions. For a general overview, see our guide to understanding medication side effects.

What is Valtrex Used For?

Valtrex is approved for the treatment and management of infections caused by specific herpes viruses. It controls symptoms and reduces viral shedding but is not a cure, as the virus remains dormant in the body.

Primary Medical Uses

• Herpes Zoster (Shingles): Treatment of acute episodes. Shingles is a painful rash caused by the reactivation of the chickenpox virus (VZV).
• Genital Herpes:
  • Initial Episode: Treatment of the first outbreak.
  • Recurrent Episodes: Treatment of subsequent outbreaks.
  • Suppressive Therapy: Daily use to reduce the frequency of recurrent outbreaks and lower the risk of transmitting the virus to sexual partners.
• Herpes Labialis (Cold Sores): Treatment of recurrent cold sores around the mouth caused by HSV-1.
• Chickenpox (Varicella): Treatment of chickenpox in immunocompetent pediatric patients when initiated within 24 hours of rash onset.

Important Limitations

Valtrex is only effective against viruses in the herpes family. It will not work for bacterial infections, influenza, the common cold, or COVID-19. The medication works best when started at the very beginning of an outbreak.

Important Safety Concerns and Considerations

Kidney Function and Hydration

The most significant safety concern with Valtrex is its potential effect on the kidneys. In rare cases, high doses in dehydrated patients or those with poor kidney function can lead to acute kidney injury due to crystal formation in the renal tubules. This risk underscores the critical importance of maintaining excellent hydration during treatment and ensuring proper dosage adjustment for patients with renal impairment.

Thrombotic Thrombocytopenic Purpura/Hemolytic Uremic Syndrome (TTP/HUS)

This is a very rare but serious condition involving blood clotting and kidney failure that has been reported in some patients with advanced HIV disease or following organ transplant who were taking high doses of valacyclovir. Symptoms include fever, easy bruising/bleeding, unusual tiredness, and paleness. Immediate medical evaluation is required.

Neurological Adverse Reactions

Agitation, hallucinations, confusion, tremors, and seizures have been reported, primarily in older adult patients and those with impaired kidney function. These symptoms usually resolve after discontinuing the drug. Patients and caregivers should be aware of these potential effects.

Contraception and Pregnancy

While Valtrex is often used in pregnancy, women of childbearing potential should discuss their plans with a doctor. Using effective contraception during treatment may be advised, though the drug itself does not affect hormonal contraception.

Viral Resistance and Treatment Failure

Although uncommon, strains of herpes virus resistant to valacyclovir/acyclovir can emerge, particularly in immunocompromised patients who have received prolonged therapy. A lack of response to treatment should be reported to a healthcare provider.

Critical Warnings for Valtrex Use

Dosage Adjustment for Renal Impairment

Valtrex dosage must be reduced in patients with impaired kidney function (low creatinine clearance). Failure to adjust the dose can lead to excessive drug accumulation, significantly increasing the risk of the serious neurological and kidney side effects described above. Your doctor will calculate the appropriate dose based on your kidney function.

Monitoring for Neurological Symptoms

Patients, especially the elderly and those with any degree of renal dysfunction, should be closely monitored for signs of central nervous system toxicity. Family members or caregivers should also be informed to watch for symptoms like confusion, hallucinations, or speech problems. These are reversible upon discontinuation of the drug.

Use in Immunocompromised Patients

Patients with advanced HIV infection, bone marrow transplant, or kidney transplant recipients who are treated with high doses for herpes zoster have experienced TTP/HUS. These patients require close medical supervision.

Early Treatment Initiation

To be most effective in treating an outbreak, Valtrex should be initiated at the earliest possible moment—ideally within the first 48-72 hours of symptom or lesion appearance. Delayed initiation reduces clinical benefit.

Sun Exposure as a Trigger

Ultraviolet (UV) light from the sun is a common trigger for outbreaks of herpes labialis (cold sores). Using effective sun protection on the lips and face can be an important part of preventing recurrences.

Valtrex Dosage Information

Dosage is determined by the treating physician based on the specific infection being treated and the patient’s kidney function. All dosages require adjustment for renal impairment. The following are standard doses for adults with normal kidney function.

Important Administration Notes

• Renal Impairment: Dosage frequency and/or amount must be reduced according to creatinine clearance. Consult prescribing information or a doctor.
• Hemodialysis Patients: A dose is recommended after each dialysis session, as valacyclovir is removed by dialysis.
• Missed Dose: Do not double the dose. Take the next dose at the regular time.

Drug Interactions with Valtrex

Valtrex has a low potential for clinically significant drug interactions. The primary interaction of concern involves other medications that affect kidney function.

Always inform your healthcare provider about all prescription, over-the-counter, and herbal products you are taking.

Additional Information

Historical Fact

Valacyclovir was developed as a prodrug of acyclovir to overcome the latter’s poor oral bioavailability. It received FDA approval in the United States in 1995. The development of valacyclovir represented a significant advancement in antiviral therapy by providing the efficacy of acyclovir with a far more patient-friendly dosing regimen, greatly improving treatment adherence.

Obtaining Medication Safely

Valtrex is a prescription medication. It should only be obtained with a valid prescription from a licensed healthcare provider. Be cautious of online sources that sell prescription drugs without a prescription, as they may provide counterfeit or substandard products. This is particularly relevant for medications treating conditions like genital herpes, where patients may seek discretion. For guidance, see our resource on buying medicines online safely.

Reporting Side Effects

You can report negative side effects of prescription drugs to the FDA at 1-800-FDA-1088 or visit www.fda.gov/medwatch.

References and Medical Sources

1. U.S. Food and Drug Administration (FDA). Valtrex (valacyclovir hydrochloride) Caplets Prescribing Information. [Revised 2008]. https://www.accessdata.fda.gov/drugsatfda_docs/label/2008/020487s014lbl.pdf
2. MedlinePlus. Valacyclovir. U.S. National Library of Medicine; [Updated 2022]. https://medlineplus.gov/druginfo/meds/a695010.html
3. Centers for Disease Control and Prevention (CDC). Sexually Transmitted Infections Treatment Guidelines, 2021: Genital HSV Infections. [Updated 2021]. https://www.cdc.gov/std/treatment-guidelines/herpes.htm
4. Drugs.com. Valacyclovir Professional Monograph. Drugs.com; [Updated 2024]. https://www.drugs.com/monograph/valacyclovir.html

Disclaimer: The information on this site is provided for informational purposes only and is not medical advice. It does not replace professional medical consultation, diagnosis, or treatment. Do not self-medicate based on the information presented on this site. Always consult with a doctor or other qualified healthcare professional before making any decisions about your health.