Valacyclovir pills 500mg 10pcs

Pharmacological action

Antiviral agent of the group of nucleoside analogues. Valacyclovir is the L-valine ester of acyclovir, thus being a prodrug.

After absorption into the blood, valacyclovir is almost completely converted to acyclovir by the hepatic enzyme valacyclovir hydrolase. Acyclovir formed from valacyclovir, in turn, penetrates into virus-affected cells, where it is converted to monophosphate under the influence of the viral enzyme thymidine kinase, and then, under the influence of cellular kinases, to diphosphate and active triphosphate.

Acyclovir triphosphate inhibits DNA polymerase and thus disrupts viral DNA replication. In addition, disruption of viral DNA replication may result from the incorporation of acyclovir into its structure.

Thus, the high selectivity of valacyclovir in relation to tissues affected by the virus is explained by the fact that the first stage of the chain of phosphorylation reactions is mediated by an enzyme produced by the virus itself.

Active against Herpes simplex viruses types 1 and 2, Varicella zoster, cytomegalovirus, Epstein-Barr virus, human herpes virus 6.

Pharmacokinetics

After oral use, valacyclovir is well absorbed from the gastrointestinal tract, quickly and almost completely converted to acyclovir and L-valine under the action of the enzyme valacyclovir hydrolase.

After a single dose of 0.25-2 g of valacyclovir, the Cmax of acyclovir in healthy volunteers with normal renal function averages 10-37 mmol (2.2-8.3 mcg / ml) and is reached in 1-2 hours.

The bioavailability of acyclovir when taking more than 1 g of valacyclovir is 54% and does not depend on food intake.

Cmax of valacyclovir in plasma is only 4% of the acyclovir level and is reached on average 30-100 minutes after taking the drug; after 3 hours, the Cmax level remains the same or decreases.

The binding of valacyclovir to plasma proteins is very low-15%.

In patients with normal renal function, the T1/2 of acyclovir is about 3 hours. Valacyclovir is excreted in the urine, mainly in the form of acyclovir (more than 80% of the dose) and its metabolite 9-carboxymethoxymethylguanine, and less than 1% of the drug is excreted unchanged.

In patients with end-stage renal failure, the T1/2 of acyclovir is approximately 14 hours.

In late pregnancy, the sustained daily AUC after taking 1 g of valacyclovir was approximately 2 times higher than that when taking acyclovir at a dose of 1.2 g/day.

In organ transplant recipients receiving valacyclovir at a dose of 2 g 4 times / day, the Cmax of acyclovir is equal to or exceeds that of healthy volunteers receiving the same dose of valacyclovir, and their daily AUC values are significantly higher.

Indications

Treatment and prevention of infectious diseases caused by Herpes zoster.

Prevention of cytomegalovirus infection that develops during organ transplantation.

Contraindications

Hypersensitivity to valacyclovir, acyclovir.

Side effects

of the digestive system:  nausea, discomfort, abdominal pain, vomiting, diarrhea, anorexia; rarely-transient increase in liver tests.

From the central nervous system:  headache, fatigue, dizziness, confusion, hallucinations; rarely-impaired consciousness; in some cases – coma (usually in patients with impaired renal function or other predisposing factors).

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

Other services:  rarely-thrombocytopenia, dyspnea, impaired renal function, photosensitization.

Interaction

No clinically significant interaction of valacyclovir with other medicinal products has been established.

Acyclovir in unchanged form enters the urine as a result of active tubular secretion.

Any drugs that are prescribed simultaneously with it and compete for this elimination mechanism can cause an increase in the concentration of valacyclovir in plasma.

Cimetidine and drugs that block tubular secretion, when prescribed after taking valacyclovir at a dose of 1 g, increase the AUC for acyclovir and reduce its renal clearance.

Concomitant use of acyclovir and an inactive metabolite of mycophenolate mofetil (an immunosuppressant used in transplantation) resulted in an increase in the AUC of acyclovir and mycophenolate mofetil.

Concomitant use of valacyclovir with drugs that impair renal function (including cyclosporine, tacrolimus) may cause deterioration of renal function.

How to take, course of use and dosage

When taken orally, the single dose for adults is 0.25-2 g. The frequency of use and duration of treatment depend on the indications.

Patients with severe renal impairment need to adjust the dosage regimen.

Special instructions

Elderly patients should increase their fluid intake during treatment.

Patients with renal insufficiency have an increased risk of neurological complications when taking valacyclovir.

Use with caution in patients with liver disease.

There is no clinical experience of its use in children.

Active ingredient

Valacyclovir

Conditions of release from pharmacies

By prescription

Dosage form

Tablets

Description

For adults as prescribed by a doctor, For adults

Indications

Cold, Cytomegalovirus Infection, Herpes