Zelitrex Drug Information [ GlaxoSmithKline ]

Table of content

Zelitrex category:

• Human
• Nucleosides and Nucleotides

Active ingredients:

• Valacyclovir Hydrochloride

Zelitrex companies and manufacturers:

• GlaxoSmithKline

General Information

Zelitrex forms, composition and dosages:

• Tablet, Film-Coated; Oral; Valacyclovir Hydrochloride 500 mg

Indications, usages and classification codes:

• J05AB11 - Valaciclovir

There is an additional general information about this medication active ingredient valacyclovir (valaciclovir):

Pharmacological action

This medication is an antiviral agent of nucleosides group. Valacyclovir (valaciclovir) 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.

Pharmacokinetics

After oral administration valaciclovir 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 C_max 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.
C_max of valaciclovir in plasma is only 4% of the acyclovir and achieved an average of 30-100 minutes after ingestion, after 3 h C_max level remains unchanged or declines.
Binding of valaciclovir to plasma proteins is very low - 15%.

Why is Zelitrex prescribed?

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 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.

Zelitrex side effects

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 (usually in patients with impaired renal function or other predisposing factors).
Allergic reactions: rarely - rash, urticaria, pruritus, angioedema, anaphylaxis.
Other: rarely - thrombocytopenia, dyspnea, renal dysfunction, photosensitivity.

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 this medication 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 (which is a metabolite of valaciclovir) is excreted in breast milk at concentrations of 0.6-4.1 times higher than its concentration in plasma. T_1/2 of acyclovir in breast milk is 2.8 h, comparable to the T_1/2 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.

Zelitrex 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 (immunosuppressant, used in transplantation) observed an increase in AUC of acyclovir and mycophenolate mofetil.
Simultaneous administration with drugs violating renal function (including cyclosporine, tacrolimus) possibly worsening renal function.

Zelitrex in case of emergency / overdose

Symptoms: sedimentation of acyclovir in renal tubules.
Treatment: dialysis (when acute renal failure and anuria).

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