Valaciclovir Viatris
Antiviral medication for herpes simplex, shingles, cold sores, and CMV prevention
Valaciclovir Viatris is a prescription antiviral medication containing valaciclovir hydrochloride hydrate, a prodrug of aciclovir. It is used to treat and prevent infections caused by herpes simplex virus (HSV), varicella-zoster virus (VZV), and cytomegalovirus (CMV). Available as 500 mg film-coated tablets, it is indicated for adults and adolescents over 12 years of age for shingles, genital herpes, cold sores, HSV eye infections, and CMV prevention after organ transplantation.
Quick Facts
Key Takeaways
- Valaciclovir Viatris is an antiviral prodrug of aciclovir with 3–5 times better oral absorption, allowing less frequent dosing for herpes simplex, shingles, cold sores, and CMV prevention.
- Dosage varies by indication: 1000 mg three times daily for shingles, 500 mg twice daily for genital herpes, and 2000 mg twice in one day for cold sores.
- Common side effects include headache, nausea, and dizziness; serious but rare effects include kidney problems and neurological symptoms, especially in patients with renal impairment.
- Adequate hydration during treatment is essential to reduce the risk of kidney-related side effects, particularly in elderly patients and those with kidney problems.
- This medicine is not recommended for children under 12 years or during pregnancy unless the benefits clearly outweigh the risks, as determined by a physician.
What Is Valaciclovir Viatris and What Is It Used For?
Valaciclovir Viatris contains the active substance valaciclovir hydrochloride hydrate, which belongs to a group of medicines known as antivirals. Once taken by mouth, valaciclovir is rapidly and almost completely converted to aciclovir and the amino acid L-valine in the gastrointestinal tract and liver. Aciclovir is a potent and selective inhibitor of herpes viruses, targeting the viral DNA polymerase enzyme to halt viral replication without significantly affecting normal human cells.
The key advantage of valaciclovir over aciclovir itself is its substantially improved oral bioavailability. While oral aciclovir achieves only about 10–20% absorption, valaciclovir provides bioavailability of approximately 54%, effectively delivering aciclovir plasma concentrations comparable to those achieved with intravenous aciclovir. This pharmacokinetic improvement allows for less frequent dosing and greater patient convenience, which can improve treatment adherence.
Valaciclovir Viatris is indicated for the following conditions in adults and, for most indications, in adolescents aged 12 years and older:
- Herpes zoster (shingles) – Treatment of shingles in adults. Early initiation of treatment (within 72 hours of rash onset) is associated with better outcomes, including reduced severity and duration of pain.
- HSV skin infections and genital herpes – Treatment of initial and recurrent episodes, as well as suppressive therapy to help prevent recurrences and reduce the risk of transmission to sexual partners.
- Cold sores (herpes labialis) – Treatment of cold sores in adults and adolescents over 12 years. High-dose, short-course therapy can reduce the duration and severity of outbreaks.
- CMV prevention after organ transplantation – Prophylaxis of cytomegalovirus infection and disease following solid organ transplantation, a critical application since CMV reactivation is a significant cause of morbidity and mortality in transplant recipients.
- Recurrent HSV eye infections – Treatment and prevention of recurring herpes simplex eye infections in adults and adolescents over 12 years.
Valaciclovir acts through a highly specific mechanism. After conversion to aciclovir, the drug requires phosphorylation by the viral enzyme thymidine kinase to become activated. This means aciclovir is preferentially activated in virus-infected cells, providing selectivity that minimises toxicity to uninfected cells. Once tri-phosphorylated, aciclovir triphosphate competes with the natural nucleotide deoxyguanosine triphosphate for incorporation into the growing viral DNA chain, causing chain termination and halting viral replication.
Valaciclovir does not cure herpes infections but effectively controls symptoms, reduces the frequency and severity of outbreaks, and can significantly decrease the risk of viral transmission. Herpes viruses remain latent in nerve ganglia and can reactivate. Continuous suppressive therapy may be recommended for patients with frequent recurrences.
What Should You Know Before Taking Valaciclovir Viatris?
Contraindications
You must not take Valaciclovir Viatris if you are allergic (hypersensitive) to valaciclovir or aciclovir, or to any of the other ingredients in this medicine (listed in the composition section below). Since valaciclovir is converted to aciclovir in the body, a known allergy to either substance is a contraindication to use. Additionally, do not take this medicine if you have previously developed a widespread rash associated with fever, enlarged lymph nodes, elevated liver enzyme levels, and/or eosinophilia (a condition known as Drug Reaction with Eosinophilia and Systemic Symptoms, or DRESS) after taking valaciclovir.
If you are unsure whether any of these apply to you, speak with your doctor or pharmacist before starting treatment.
Warnings and Precautions
Talk to your doctor or pharmacist before taking Valaciclovir Viatris if any of the following apply to you:
- Kidney problems: Dose adjustment is necessary for patients with impaired renal function. Your doctor will determine the appropriate dose based on your creatinine clearance. Adequate fluid intake is particularly important to reduce the risk of renal complications.
- Liver problems: Although valaciclovir undergoes hepatic metabolism during its conversion to aciclovir, clinically significant liver impairment has not been shown to require dose adjustments. However, your doctor should be informed of any liver conditions.
- Age over 65 years: Elderly patients are more likely to have reduced kidney function, which may require dose adjustment. They are also at greater risk for neurological side effects such as confusion, agitation, and drowsiness.
- Weakened immune system: Immunocompromised patients, including those with HIV/AIDS or taking immunosuppressive therapy, may require closer monitoring and potentially different dosing strategies.
Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) has been reported with valaciclovir use. DRESS initially presents with flu-like symptoms and a facial rash, followed by widespread rash and high fever, elevated liver enzymes (found in blood tests), an increase in a type of white blood cell (eosinophilia), and enlarged lymph nodes. If you develop a rash accompanied by fever and enlarged lymph nodes, stop taking valaciclovir and contact your doctor or seek medical attention immediately.
Preventing Transmission of Genital Herpes
If you are taking Valaciclovir Viatris to treat or suppress genital herpes, or if you have previously had genital herpes, it is essential to practice safe sex, including the use of condoms, even during suppressive therapy. Valaciclovir significantly reduces but does not completely eliminate the risk of HSV transmission to sexual partners. You should avoid sexual contact entirely if you have active genital sores or blisters. Studies have shown that daily suppressive therapy with valaciclovir reduces the risk of genital herpes transmission to an uninfected partner by approximately 50%, and condom use provides additional protection.
Pregnancy and Breastfeeding
Valaciclovir Viatris is not generally recommended for use during pregnancy. If you are pregnant, breastfeeding, think you may be pregnant, or are planning to have a baby, ask your doctor for advice before using this medicine. Your doctor will weigh the benefit to you against the risk to your child. Animal studies have not shown direct harmful effects on the foetus, but there are limited data from clinical trials in pregnant women. Aciclovir (the active metabolite) is excreted in breast milk at concentrations approximately 0.6–4.1 times the corresponding maternal plasma levels, but the dose received by a breastfed infant would represent less than 2% of the therapeutic paediatric dose.
Driving and Using Machines
Valaciclovir may cause side effects such as dizziness, confusion, drowsiness, or hallucinations that could impair your ability to drive or operate machinery. Do not drive or use machines unless you are sure you are not affected. You are personally responsible for assessing whether you are fit to perform these activities. If you experience any of these neurological effects, avoid driving and operating machinery until the symptoms resolve.
Use in Children Under 12 Years
Valaciclovir is not recommended for use in children under 12 years of age due to insufficient data on safety and efficacy in this age group. For paediatric patients under 12, other formulations of aciclovir (such as oral suspension) may be more appropriate, as determined by the treating physician.
How Does Valaciclovir Viatris Interact with Other Drugs?
Tell your doctor or pharmacist if you are taking, have recently taken, or might take any other medicines, including over-the-counter products and herbal supplements. Drug interactions with valaciclovir primarily involve the renal pathway, since aciclovir is predominantly eliminated by the kidneys through both glomerular filtration and active tubular secretion.
The following medications are of particular clinical concern when taken concomitantly with valaciclovir:
Major Interactions
| Drug / Drug Class | Interaction Mechanism | Clinical Significance |
|---|---|---|
| Aminoglycosides (e.g., gentamicin) | Additive nephrotoxicity; both drugs are renally cleared | Monitor renal function closely; dose adjustment may be needed |
| Ciclosporin | Increased risk of renal impairment; ciclosporin is nephrotoxic | Monitor renal function; particularly important in transplant patients |
| Tacrolimus | Increased risk of nephrotoxicity and neurotoxicity | Monitor renal function and neurological status; adjust doses if needed |
| Methotrexate | Competition for renal tubular secretion | Potential for increased plasma levels of both drugs; monitor closely |
| Mycophenolate mofetil | Competition for renal tubular secretion; increased plasma levels of both drugs | Commonly co-prescribed in transplant recipients; monitor renal function |
Other Notable Interactions
| Drug / Drug Class | Interaction Mechanism | Clinical Significance |
|---|---|---|
| Cimetidine | Inhibits renal tubular secretion of aciclovir, increasing plasma concentrations | Aciclovir AUC increases by approximately 25%; usually not clinically significant in patients with normal renal function |
| Probenecid | Inhibits renal tubular secretion of aciclovir | Aciclovir AUC increases by approximately 40%; monitor for aciclovir-related adverse effects |
| Iodinated contrast media | Additive nephrotoxicity risk | Ensure adequate hydration; monitor renal function |
| Foscarnet | Additive nephrotoxicity; both are renally eliminated antivirals | Avoid combination if possible; monitor renal function if co-administered |
| Pentamidine | Additive nephrotoxicity | Monitor renal function closely during concomitant use |
It is especially important to tell your doctor about all medications you are taking if you are using Valaciclovir Viatris for the treatment of shingles or following an organ transplantation, as these situations often involve higher doses and longer treatment durations, increasing the potential for drug interactions.
Unlike many other antiviral agents, valaciclovir is not metabolised by the cytochrome P450 enzyme system, which means it has a relatively low potential for hepatic drug-drug interactions. The primary interaction concern is renal, so any co-administered nephrotoxic drugs or drugs competing for tubular secretion warrant additional monitoring.
What Is the Correct Dosage of Valaciclovir Viatris?
Always take this medicine exactly as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure. Your doctor will determine the appropriate dose based on the condition being treated, its severity, and your individual circumstances including kidney function.
Adults
| Indication | Dose | Frequency | Duration |
|---|---|---|---|
| Herpes zoster (shingles) | 1000 mg (two 500 mg tablets) | Three times daily | 7 days |
| Cold sores (herpes labialis) | 2000 mg (four 500 mg tablets) | Twice daily (12 hours apart) | 1 day only |
| Genital herpes – initial episode | 500 mg (one 500 mg tablet) | Twice daily | 5–10 days |
| Genital herpes – recurrence | 500 mg (one 500 mg tablet) | Twice daily | 3–5 days |
| Genital herpes – suppression | 500 mg (one 500 mg tablet) | Once daily | As directed by physician |
| CMV prophylaxis (post-transplant) | 2000 mg (four 500 mg tablets) | Four times daily (every 6 hours) | Approx. 90 days post-surgery |
For the treatment of shingles, it is important to start therapy as early as possible, ideally within 72 hours of the appearance of the rash. Clinical studies have demonstrated that earlier initiation correlates with better outcomes, including reduced duration and severity of post-herpetic neuralgia (persistent nerve pain after the rash resolves).
For cold sore treatment, the second dose should be taken approximately 12 hours after the first dose, but not sooner than 6 hours. Treatment is most effective when started at the very first sign of a cold sore, such as tingling, itching, or burning at the lip.
For suppressive therapy of frequently recurring genital herpes, some patients with very frequent recurrences (10 or more episodes per year) may benefit from a divided dose of 250 mg twice daily. Since Valaciclovir Viatris is only available in 500 mg tablets, lower-strength valaciclovir products may be needed for this regimen. Your doctor will advise you on the most appropriate option.
Adolescents (12 Years and Older)
Adolescents aged 12 years and older generally receive the same doses as adults for the treatment of cold sores, genital herpes, HSV skin infections, recurrent HSV eye infections, and CMV prophylaxis. The treatment of shingles with valaciclovir is approved for adults only. Valaciclovir is not recommended for children under 12 years due to insufficient safety and efficacy data.
Elderly Patients and Those with Kidney Problems
Your doctor may adjust your dose of Valaciclovir Viatris if you are over 65 years old, have a weakened immune system, or have kidney problems. Dose reduction is based on creatinine clearance levels, and your doctor will determine the appropriate adjustment. During treatment, it is critically important to drink water regularly throughout the day. Adequate hydration helps to reduce side effects that can affect the kidneys or nervous system.
Your doctor will monitor you for signs of renal or neurological adverse effects. Neurological side effects may include feeling confused, agitated, unusually sleepy, or drowsy. These effects are generally reversible upon discontinuation or dose reduction.
How to Take This Medicine
- Take this medicine by mouth.
- Swallow the tablets whole with water. Do not crush, chew, or break the tablets.
- Take Valaciclovir Viatris at the same time(s) each day for consistent blood levels.
- The medicine can be taken with or without food.
- Drink plenty of water throughout the day, especially if you are elderly or have kidney problems.
Missed Dose
If you forget to take a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a forgotten one. Consistency in dosing helps maintain effective antiviral drug levels in the body.
Overdose
If you have taken more Valaciclovir Viatris than you should, or if a child has accidentally swallowed this medicine, contact your doctor, hospital, or poison control centre immediately for risk assessment and advice. Valaciclovir is usually not harmful if slightly more than the prescribed dose is taken, but excessive amounts over several consecutive days can cause nausea, vomiting, confusion, agitation, unusual drowsiness, hallucinations (seeing, feeling, or hearing things that are not there), kidney problems (manifesting as very low or no urine output), or loss of consciousness (coma). Bring the medicine packaging with you when seeking medical attention.
Stopping Treatment
Do not stop taking this medicine without first consulting your doctor, even if you feel better. For conditions like shingles and initial genital herpes episodes, completing the full course of treatment is important to maximise therapeutic benefit and reduce the risk of complications. For suppressive therapy, your doctor will advise you on the appropriate duration and when it is safe to discontinue.
What Are the Side Effects of Valaciclovir Viatris?
Like all medicines, Valaciclovir Viatris can cause side effects, although not everybody gets them. Side effects most commonly occur at the start of treatment and generally become milder or resolve within a few weeks. Sometimes it can be difficult to distinguish between symptoms of the underlying illness and a side effect of the medication.
Contact your doctor or go to the nearest emergency department immediately if you experience any of the following serious side effects. Stop taking this medicine:
- Severe allergic reactions (anaphylaxis) with rapid onset of flushing, itchy skin rash, swelling of the lips, face, neck, or throat causing breathing difficulty (angioedema), or a drop in blood pressure leading to collapse
- Kidney problems manifesting as very low or no urine output
- Seizures (convulsions)
- Altered brain function (encephalopathy) or loss of consciousness (coma)
- Confused or disturbed thoughts
- Widespread rash with fever, enlarged lymph nodes, and feeling unwell (possible DRESS syndrome)
The following side effects have been reported with valaciclovir, categorised by frequency:
Very Common
Affects more than 1 in 10 people
- Headache
Common
Affects up to 1 in 10 people
- Nausea
- Dizziness
- Vomiting
- Diarrhea
- Skin reactions, including after sun exposure (photosensitivity)
- Skin rash
Uncommon
Affects up to 1 in 100 people
- Confusion
- Hallucinations (seeing or hearing things that are not there)
- Drowsiness
- Tremor (shaking)
- Feeling of agitation
- Shortness of breath (dyspnoea)
- Stomach discomfort
- Skin rash, sometimes itchy; hives (urticaria)
- Lower back pain (kidney pain)
- Blood in the urine
- Decreased white blood cell count (leucopenia)
- Decreased platelet count (thrombocytopenia)
- Elevated liver enzymes
Rare
Affects up to 1 in 1,000 people
- Severe allergic reactions (anaphylaxis)
- Kidney problems (reduced or no urine output)
- Seizures (convulsions)
- Altered brain function (encephalopathy)
- Loss of consciousness (coma)
- Unsteady gait or poor coordination (ataxia)
- Slow and slurred speech (dysarthria)
Not Known
Frequency cannot be estimated from available data
- DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms) – widespread rash, high fever, elevated liver enzymes, blood abnormalities, enlarged lymph nodes
- Inflammation of the kidneys (tubulointerstitial nephritis)
The uncommon and rare neurological side effects (confusion, hallucinations, drowsiness, tremor, ataxia, dysarthria, agitation) occur primarily in patients with kidney problems, elderly patients, or organ transplant recipients taking high doses of valaciclovir (8 g or more per day). These effects are usually reversible when Valaciclovir Viatris is discontinued or the dose is reduced. If you experience any neurological symptoms, contact your doctor promptly.
If you notice any side effects not listed here, or if any side effect becomes severe, please tell your doctor or pharmacist. Reporting suspected adverse reactions after the medicine has been authorised is important, as it permits ongoing monitoring of the medicine’s benefit-risk balance.
How Should You Store Valaciclovir Viatris?
Keep this medicine out of the sight and reach of children at all times. Store the tablets in their original packaging to protect them from moisture. Do not use this medicine after the expiry date stated on the carton and blister pack after “EXP”. The expiry date refers to the last day of that month.
This medicine does not require any special storage conditions. It should be stored at room temperature, away from direct heat and light. There is no need to refrigerate valaciclovir tablets.
Medicines should not be disposed of via wastewater or household waste. Ask your pharmacist how to dispose of medicines you no longer use. These measures help to protect the environment. Never give your medicines to other people, even if their symptoms appear similar to yours, as the same medicine may not be appropriate for them.
What Does Valaciclovir Viatris Contain?
The active substance is valaciclovir hydrochloride hydrate. Each film-coated tablet contains valaciclovir hydrochloride hydrate equivalent to 500 mg of valaciclovir (the therapeutically active moiety).
Inactive Ingredients
Tablet core: Microcrystalline cellulose, crospovidone, povidone, and magnesium stearate. These excipients serve as fillers, disintegrants, binders, and lubricants respectively, ensuring the tablet has appropriate mechanical properties and disintegrates properly after ingestion.
Film coating: Titanium dioxide (E171), macrogol 400, polysorbate 80 (E433), and hypromellose (E464). The film coating provides a smooth, easy-to-swallow surface, protects the active ingredient from moisture, and masks the taste of the tablet core.
Appearance and Pack Sizes
Valaciclovir Viatris 500 mg tablets are white to off-white, capsule-shaped, biconvex film-coated tablets. They are marked “VC 500” on one side and “G” on the other side. The tablets are available in blister packs of 10, 21, 24, 30, 42, 60, 90, 100, and 112 tablets. Not all pack sizes may be marketed in every country.
Frequently Asked Questions About Valaciclovir Viatris
Valaciclovir Viatris is an antiviral medication used to treat herpes zoster (shingles) in adults, genital herpes and HSV skin infections (treatment and suppression), cold sores (herpes labialis), and to prevent CMV infection after organ transplantation. It is also used for recurrent HSV eye infections. It works by stopping the replication of herpes viruses in the body.
Take the tablets exactly as prescribed by your doctor. Swallow them whole with water – do not crush or chew them. The dose depends on the condition being treated: 1000 mg three times daily for shingles (7 days), 500 mg twice daily for genital herpes (3–10 days), or 2000 mg twice in one day for cold sores. Drink plenty of water during treatment, especially if you are elderly or have kidney problems.
The most common side effect is headache, affecting more than 1 in 10 people. Other common side effects (affecting up to 1 in 10) include nausea, dizziness, vomiting, diarrhea, skin rash, and photosensitivity. These side effects usually occur at the start of treatment and tend to improve within a few weeks. Uncommon but important side effects include confusion, hallucinations, and drowsiness, particularly in elderly patients or those with kidney problems.
Valaciclovir is not generally recommended during pregnancy. If you are pregnant, breastfeeding, think you may be pregnant, or are planning a pregnancy, consult your doctor before taking this medicine. Your doctor will carefully weigh the benefits to you against any potential risks to your baby. Animal studies have not shown direct harmful effects, but human data from clinical trials is limited.
Valaciclovir is a prodrug of aciclovir – it is converted to aciclovir in the body after absorption. The key advantage is that valaciclovir has 3–5 times better oral bioavailability than aciclovir, meaning more of the drug reaches the bloodstream. This allows for less frequent dosing (e.g., three times daily for shingles instead of five times daily with aciclovir). Both medications ultimately work through the same mechanism against herpes viruses.
Valaciclovir begins working within hours of taking the first dose, as it is rapidly absorbed and converted to aciclovir. For cold sores, starting treatment at the very first sign of symptoms (tingling or itching) can prevent or significantly shorten an outbreak. For shingles, treatment is most effective when started within 72 hours of the rash appearing. For suppressive therapy of genital herpes, it may take several weeks to see the full preventive benefit, but the antiviral effect begins immediately.
References
This article is based on the following peer-reviewed sources and authoritative medical guidelines:
- European Medicines Agency (EMA). Valaciclovir – Summary of Product Characteristics (SmPC). Updated 2025. Available from EMA product information database.
- World Health Organization (WHO). WHO Model List of Essential Medicines – 23rd List. Geneva: WHO; 2023. Aciclovir (from which valaciclovir derives) is listed as an essential antiviral medicine.
- Tyring SK, Baker D, Snowden W. Valacyclovir for herpes simplex virus infection: long-term safety and sustained efficacy after 20 years' experience with acyclovir. J Infect Dis. 2002;186(Suppl 1):S40–S46.
- Beutner KR, Friedman DJ, Forszpaniak C, Andersen PL, Wood MJ. Valaciclovir compared with acyclovir for improved therapy for herpes zoster in immunocompetent adults. Antimicrob Agents Chemother. 1995;39(7):1546–1553.
- Corey L, Wald A, Patel R, et al. Once-daily valacyclovir to reduce the risk of transmission of genital herpes. N Engl J Med. 2004;350(1):11–20.
- British National Formulary (BNF). Valaciclovir. National Institute for Health and Care Excellence (NICE). Updated 2025.
- Lowance D, Neumayer HH, Legendre CM, et al. Valacyclovir for the prevention of cytomegalovirus disease after renal transplantation. N Engl J Med. 1999;340(19):1462–1470.
- Patel R, Bodsworth NJ, Woolley P, et al. Valaciclovir for the suppression of recurrent genital HSV infection: a placebo controlled study of once daily therapy. Genitourin Med. 1997;73(2):105–109.
Editorial Team
This article was written and reviewed by the iMedic Medical Editorial Team, comprising licensed physicians and pharmacologists with expertise in infectious diseases, antiviral therapy, and clinical pharmacology. All content follows the GRADE evidence framework and is reviewed according to international guidelines from the WHO, EMA, FDA, and BNF.
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