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Valacyclovir uses

Pharmacological action

Valacyclovir is an antiviral agent of nucleosides group. Valacyclovir is the L-valine ester of acyclovir being thus a prodrug.

After absorption into the blood valacyclovir almost completely converted to acyclovir under the influence of hepatic enzyme valacyclovir-hydrolase. In turn Acyclovir formed from valacyclovir affected by the virus penetrates cells where under the influence of the viral enzyme thymidine kinase converted into a monophosphate, then under the influence of cellular kinases - in the active diphosphate and triphosphate. Acyclovir triphosphate inhibits DNA polymerase and thus violates the replication of virus DNA. In addition the violation of the replication of viral DNA may be a result of incorporation of acyclovir into its structure. Thus the high selectivity of valacyclovir for tissues infected with a virus, because the stage I reaction chain phosphorylation mediated by the enzyme produced by the virus.

This drug is active against Herpes Simplex virus types 1 and 2, Varicella Zoster, cytomegalovirus, Epstein-Barr virus, human herpes virus 6.


After oral administration Valacyclovir is well absorbed from the gastrointestinal tract rapidly and almost completely converted to acyclovir and L-valine by the enzyme valacyclovir-hydrolase.

After a single dose of 0.25-2 g of valacyclovir Cmax of acyclovir in healthy volunteers with normal renal function is an average of 10-37 mmol (2.2-8.3 mg / ml) and achieved in 1-2 hours.

Bioavailability of acyclovir when receiving from 1 g of valaciclovir is 54% and is independent of ingestion.

Cmax of valaciclovir in plasma is only 4% of the acyclovir and achieved an average of 30-100 minutes after ingestion, after 3 h Cmax level remains unchanged or declines.

Binding of valaciclovir to plasma proteins is very low - 15%.

Why is Valacyclovir prescribed?

Valacyclovir is used for the treatment and prevention of infectious diseases caused by Herpes Zoster.

Prevention of cytomegalovirus infection developing in organ transplantation.


Dosage and administration

For oral administration a single Valacyclovir dose for adults is 0.25-2 g. Frequency of admission and length of treatment depend on the evidence.

For patients with severely impaired renal function requires correction dosing regimen.

Valacyclovir side effects, adverse reactions

Digestive system: nausea, discomfort, abdominal pain, vomiting, diarrhea, anorexia; rare - transient increase of indicators of liver samples.

CNS: headache, fatigue, dizziness, confusion, hallucinations; rare - impaired consciousness, in some cases - coma.

Allergic reactions: rarely - rash, urticaria, pruritus, angioedema, anaphylaxis.

Other: rarely - thrombocytopenia, dyspnea, renal dysfunction, photosensitivity.

Valacyclovir contraindications

Hypersensitivity to valacyclovir (valaciclovir), acyclovir.

Using during pregnancy and breastfeeding

There are no adequate and well-controlled studies safety of valaciclovir in pregnancy and lactation. Prescription of Valacyclovir for this category of patients is possible in cases where the expected benefits of therapy to the mother outweighs the potential risk to the fetus or infant. It is known that acyclovir is excreted in breast milk at concentrations of 0.6-4.1 times higher than its concentration in plasma. T1/2 of acyclovir in breast milk is 2.8 h, comparable to the T1/2 from blood plasma.

In experimental studies, valacyclovir had no teratogenic effects in rats and rabbits. For oral administration valacyclovir did not cause impaired fertility in male and female rats.

Special instructions

It is necessary to increase fluid intake for elderly patients during treatment.

Patients with kidney failure have an increased risk of neurological complications while taking Valacyclovir.

This drug used with caution in patients with liver disease.

Clinical experience in children is missing.

Valacyclovir drug interactions

Clinically significant drug interactions valacyclovir with other drugs is not established.

Acyclovir comes as unchanged in the urine through active tubular secretion. Any drugs prescribed with it at the same time and compete for the mechanism of elimination, can cause high concentrations of valaciclovir in plasma. Cimetidine and drugs that block tubular secretion in the appointment after receiving valacyclovir at a dose of 1 g of acyclovir enhance AUC rate and decrease its renal clearance.

Simultaneous administration of acyclovir with the inactive metabolite of mycophenolate mofetil observed an increase in AUC of acyclovir and mycophenolate mofetil.

Simultaneous administration of Valacyclovir with drugs violating renal function (including cyclosporine, tacrolimus) possibly worsening renal function.

Valacyclovir in case of emergency / overdose

Symptoms: sedimentation of acyclovir in renal tubules.

Treatment: dialysis (when acute renal failure and anuria).


Valacyclovir pharmaceutical active ingredients containing related brand and generic drugs:

Active ingredient is the part of the drug or medicine which is biologically active. This portion of the drug is responsible for the main action of the drug which is intended to cure or reduce the symptom or disease. The other portions of the drug which are inactive are called excipients; there role is to act as vehicle or binder. In contrast to active ingredient, the inactive ingredient's role is not significant in the cure or treatment of the disease. There can be one or more active ingredients in a drug.

Valacyclovir available forms, composition, doses:

Form of the medicine is the form in which the medicine is marketed in the market, for example, a medicine X can be in the form of capsule or the form of chewable tablet or the form of tablet. Sometimes same medicine can be available as injection form. Each medicine cannot be in all forms but can be marketed in 1, 2, or 3 forms which the pharmaceutical company decided based on various background research results.
Composition is the list of ingredients which combinedly form a medicine. Both active ingredients and inactive ingredients form the composition. The active ingredient gives the desired therapeutic effect whereas the inactive ingredient helps in making the medicine stable.
Doses are various strengths of the medicine like 10mg, 20mg, 30mg and so on. Each medicine comes in various doses which is decided by the manufacturer, that is, pharmaceutical company. The dose is decided on the severity of the symptom or disease.

Valacyclovir destination | category:

Destination is defined as the organism to which the drug or medicine is targeted. For most of the drugs what we discuss, human is the drug destination.
Drug category can be defined as major classification of the drug. For example, an antihistaminic or an antipyretic or anti anginal or pain killer, anti-inflammatory or so.

Valacyclovir Anatomical Therapeutic Chemical codes:

A medicine is classified depending on the organ or system it acts [Anatomical], based on what result it gives on what disease, symptom [Therapeutical], based on chemical composition [Chemical]. It is called as ATC code. The code is based on Active ingredients of the medicine. A medicine can have different codes as sometimes it acts on different organs for different indications. Same way, different brands with same active ingredients and same indications can have same ATC code.

Valacyclovir pharmaceutical companies:

Pharmaceutical companies are drug manufacturing companies that help in complete development of the drug from the background research to formation, clinical trials, release of the drug into the market and marketing of the drug.
Researchers are the persons who are responsible for the scientific research and is responsible for all the background clinical trials that resulted in the development of the drug.



  2. Dailymed."VALACYCLOVIR HYDROCHLORIDE: DailyMed provides trustworthy information about marketed drugs in the United States. DailyMed is the official provider of FDA label information (package inserts).". (accessed August 28, 2018).
  3. "valacyclovir". (accessed August 28, 2018).

Frequently asked Questions

Can i drive or operate heavy machine after consuming Valacyclovir?

Depending on the reaction of the Valacyclovir after taken, if you are feeling dizziness, drowsiness or any weakness as a reaction on your body, Then consider Valacyclovir not safe to drive or operate heavy machine after consumption. Meaning that, do not drive or operate heavy duty machines after taking the capsule if the capsule has a strange reaction on your body like dizziness, drowsiness. As prescribed by a pharmacist, it is dangerous to take alcohol while taking medicines as it exposed patients to drowsiness and health risk. Please take note of such effect most especially when taking Primosa capsule. It's advisable to consult your doctor on time for a proper recommendation and medical consultations.

Is Valacyclovir addictive or habit forming?

Medicines are not designed with the mind of creating an addiction or abuse on the health of the users. Addictive Medicine is categorically called Controlled substances by the government. For instance, Schedule H or X in India and schedule II-V in the US are controlled substances.

Please consult the medicine instruction manual on how to use and ensure it is not a controlled substance.In conclusion, self medication is a killer to your health. Consult your doctor for a proper prescription, recommendation, and guidiance.


Review conducted a study on Valacyclovir, and the result of the survey is set out below. It is noteworthy that the product of the survey is based on the perception and impressions of the visitors of the website as well as the views of Valacyclovir consumers. We, as a result of this, advice that you do not base your therapeutic or medical decisions on this result, but rather consult your certified medical experts for their recommendations.

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The information was verified by Dr. Rachana Salvi, MD Pharmacology

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