Zelitrex

Zelitrex Uses, Dosage, Side Effects, Food Interaction and all others data.

Valacyclovir is the hydrochloride salt of L-valyl ester of the antiviral drug acyclovir. Valacyclovir is an antiviral drug. It slows the growth and spread of the herpes virus so that the body can fight off the infection. Valacyclovir lessens the symptoms of infections and shortens the length of time of sickness. Valacyclovir is used in the treatment and suppression of genital herpes, shingles and cold sores.

Antiviral effects

Valacyclovir shows varying levels of inhibition towards herpes simplex virus types 1 (HSV-1), 2 (HSV-2), Varicella Zoster Virus (VZV), Epstein-Barr virus (EBV), and cytomegalovirus (CMV). The quantitative relationship between the cell culture susceptibility of herpesviruses to antivirals and the clinical response of humans to the same antiviral therapy has not yet been elucidated. Sensitivity testing results, described by the concentration of drug needed to inhibit the growth of the virus by 50% in cell culture (EC50), vary widely depending on various factors .

Clinical study results

Trade Name Zelitrex
Generic Valaciclovir
Valaciclovir Other Names Valaciclovir, Valaciclovirum, Valacyclovir
Type
Formula C13H20N6O4
Weight Average: 324.3357
Monoisotopic: 324.154603158
Protein binding

The binding of valacyclovir to human plasma proteins is low and ranges from 13.5% to 17.9% .

Groups Approved, Investigational
Therapeutic Class Herpes simplex & Varicella-zoster virus infections
Manufacturer
Available Country
Last Updated: September 19, 2023 at 7:00 am
Zelitrex
Zelitrex

Uses

Valacyclovir is used for the treatment of Herpes zoster (shingles). It is used for the treatment or suppression of genital herpes in immuno-competent individuals and for the suppression of recurrent genital herpes in HIV infected individuals. It is also used for the treatment of cold sores (Herpes labialis).

Zelitrex is also used to associated treatment for these conditions: Chickenpox, Cytomegalovirus (CMV) Infection, Genital Herpes, Genital herpes, initial episode, Herpes Labialis, Herpes Simplex Infection, Infection Transmission, Recurrent Genital Herpes (RGH), Shingles, Symptomatic for no more than 72 hours Herpes zoster, Safer sex practices, Chronic suppressive therapy of recurrent episodes of genital herpes

How Zelitrex works

Valacyclovir is the L-valine ester of aciclovir. It is classified as a nucleoside analog DNA polymerase enzyme inhibitor. Aciclovir is a purine (guanine) nucleoside analog is a metabolite that heavily contributes to the pharmacological actions of valacyclovir. In fact, most of valacyclovir's activity is attributed to acyclovir .

Valacyclovir is rapidly and almost completely converted in man to aciclovir and valine, likely by the enzyme valacyclovir hydrolase. Aciclovir is a selective inhibitor of the herpes viruses, possessing in vitro activity against herpes simplex viruses (HSV) type 1 and type 2, varicella zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr Virus (EBV), as well as human herpesvirus 6 (HHV-6). Aciclovir has been shown to inhibit herpes virus DNA synthesis after it has been phosphorylated to the active triphosphate form .

The first stage of drug phosphorylation for acyclovir requires activation by a virus-specific enzyme. In the case of HSV, VZV and EBV this enzyme is the viral thymidine kinase (TK), which is only found in virus-infected cells. The process of phosphorylation is completed (conversion from mono- to triphosphate) by cellular kinases. Acyclovir triphosphate competitively inhibits the virus DNA polymerase and incorporation of this agent results in DNA chain termination, stopping virus DNA synthesis and blocking virus replication . The inhibitory capabilities of acyclovir are highly selective due to the drug's strong affinity for thymidine kinase (TK).

In summary, the antiviral effects of valacyclovir are achieved in 3 ways :

1) competitive inhibition of viral DNA polymerase

2) incorporation and termination of the growing viral DNA chain

3) inactivation of the viral DNA polymerase. The higher level of antiviral activity of acyclovir against HSV compared with VZV is attributed to its more efficient phosphorylation by viral thymidine kinase (TK).

Dosage

Zelitrex dosage

Adult Dosage:

Cold Sores

: 2 grams every 12 hours for 1 day

Genital Herpes:

  • Initial episode: 1 gram twice daily for 10 days
  • Recurrent episodes: 500 mg twice daily for 3 days Suppressive therapy
  • Immunocompetent patients: 1 gram once daily
  • Alternate dose in patients with < 9 recurrences/year: 500 mg once daily
  • HIV-infected patients: 500 mg twice daily
  • Reduction of transmission: 500 mg once daily

Herpes Zoster

: 1 gram 3 times daily for 7 days

Pediatric Dosage:

  • Cold Sores (> 12 years of age): 2 grams every 12 hours for 1 day
  • Chickenpox (2 to < 18 years of age): 20 mg/kg 3 times daily for 5 days; not to exceed 1 gram 3 times daily

Side Effects

The most frequently reported adverse reactions were nausea (15%), headache (14%), vomiting (6%), dizziness (3%) and abdominal pain (3%).

Toxicity

LD50 Oral

Rat – 903.5 mg/kg

Carcinogenesis, Mutagenesis, Impairment of Fertility

Valacyclovir was noncarcinogenic in lifetime carcinogenicity assays at single daily gavage doses of valacyclovir giving plasma acyclovir concentrations equivalent to human levels in the mouse bioassay and 1.4 to 2.3 times human levels in the rat bioassay. No clinically significant difference in the incidence of tumors between treated and control animals was observed, and valacyclovir was not found to shorten the latency period of tumors. Valacyclovir was tested in 5 genetic toxicity assays. An Ames assay was negative in the absence or presence of metabolic activation. An in vitro cytogenetic study with human lymphocytes and a rat cytogenetic study was negative .

In the mouse lymphoma assay, valacyclovir was not found to be mutagenic without metabolic activation, however, in the presence of metabolic activation (76% to 88% conversion to acyclovir), valacyclovir was mutagenic. Valacyclovir was also found to be mutagenic in a mouse micronucleus assay .

Valacyclovir did not impair fertility or reproduction in rats at 6 times the normal concentrations in human plasma .

Use in pregnancy

Valacyclovir is categorized as a pregnancy category B drug. There are insufficient well-controlled studies of valacyclovir in pregnant women. The general rate of birth defects in infants exposed to acyclovir in-utero is comparable to the rate for infants measured in the general population. This drug should be used during pregnancy only if the potential benefit justifies the possible fetal risk .

Use in nursing

Acyclovir, a major metabolite of valacyclovir, was excreted in breastmilk at lower concentrations when a normal therapeutic dose of valacyclovir was administered. Exercise caution when acyclovir is used while nursing .

A note on renal function and toxicity in elderly patients

Elderly patients and patients with decreased renal function are at increased risk of valacyclovir toxicity, which can sometimes lead to central nervous system effects, such as encephalopathy, agitation, dysarthria, mania, and psychosis, among other effects. Consider reducing the dose of this drug in these populations to decrease the risk of toxicity .

Precaution

Dosage reduction is recommended when administering valacyclovir to patients with renal impairment. Similar caution should be exercised when administering valacyclovir to geriatric patients and patients receiving potentially nephrotoxic agents. The safety and efficacy of valacyclovir have not been established in immuno compromised patients other than for the suppression of genital herpes in HIVinfected patients

Interaction

No dosage adjustment is recommended when valacyclovir is coadministered with digoxin, antacids, thiazide diuretics, cimetidine or probenecid in subjects with normal renal function.

Food Interaction

  • Take with or without food.

Volume of Distribution

Cerebrospinal fluid (CSF) penetration, determined by CSF/plasma AUC ratio, is approximately 25% for aciclovir and the metabolite 8-hydroxy-aciclovir (8-OH-ACV), and approximately 2.5% for the metabolite 9-(carboxymethoxy)methylguanine .

In a study of immunocompromised pediatric patients, the volume of distribution of a 15 ml/kg dose of valacyclovir was 1.34 ± 0.65 L/kg .

Elimination Route

After oral administration, valacyclovir hydrochloride is rapidly absorbed from the gastrointestinal (GI) tract and converted to acyclovir and L-valine. The absolute bioavailability of acyclovir after administration of valacyclovir was measured at 54.5% ± 9.1% after the administration of a 1 gram oral dose of valacyclovir and a 350 mg intravenous (IV) acyclovir dose to 12 healthy subjects. Acyclovir (a metabolite of valacyclovir) bioavailability from the administration of this drug is not affected by the administration with food .

Half Life

The plasma elimination half-life of acyclovir typically averaged 2.5 to 3.3 hours in several studies of valacyclovir in volunteers with normal renal function .

Clearance

Renal clearance of acyclovir following the administration of a single 1 gram dose of valacylcovir to 12 healthy 437 volunteers was approximately 255 ± 86 mL/min, which represents 42% of total acyclovir apparent plasma clearance .

Elimination Route

After oral administration of a single 1 gram dose of radiolabeled valacyclovir to 4 healthy subjects, 46% and 47% of administered radioactivity was measured in urine and feces, respectively, over 96 hours. Acyclovir accounted for 89% of the radioactivity excreted in the urine .

Pregnancy & Breastfeeding use

Pregnancy category B. Valacyclovir was not teratogenic in rats or rabbits at 10 and 7 times human plasma levels, respectively, during the period of major organogenesis. There is no adequate and well-controlled studies of valacyclovir in pregnant women. Nursing Mothers: Unchanged valacyclovir was not detected in maternal serum, breast milk, or infant urine. Valacyclovir should be administered to a nursing mother with caution and only when indicated.

Contraindication

Valacyclovir is contraindicated in patients with a known hypersensitivity or intolerance to valacyclovir, acyclovir, or any component of the formulation.

Special Warning

Pediatric Use: Safety and effectiveness of valacyclovir in pre-pubertal pediatric patients have not been established. Elderly Use (Over 65 yr.): Elderly patients may require a dose reduction of valacyclovir due to a low body weight or disorders (renal, CNS etc.) associated with aging.

Storage Condition

Store in cool & dry place, away from children.

Innovators Monograph

You find simplified version here Zelitrex

Zelitrex contains Valaciclovir see full prescribing information from innovator Zelitrex Monograph, Zelitrex MSDS, Zelitrex FDA label

FAQ

What is Zelitrex used fot?

Zelitrex is used to treat herpes zoster (shingles) and genital herpes. .This medication is sometimes prescribed for other uses.

How safe Zelitrex is?

Zelitrex is highly effective in managing herpes. It's also an extremely safe, well studied medication.

What are the side effects of Zelitrex?

The most commonly reported side effects are:

  • headache.
  • gastrointestinal discomfort (vomiting, nausea, diarrhoea, constipation, abdominal pain, indigestion)
  • sensitivity to UV light, such as the development of a rash or sunburn, even after short exposure.

Is it safe to take Zelitrex everyday?

It's safe to take Zelitrex every day as long as you've been instructed to do so. If you miss a dose of Zelitrex, you should take the next dose as soon as possible.

Is Zelitrex safe during pregnancy?

Zelitrex in the first trimester of pregnancy was not associated with an increased risk of major birth defects.Long-term suppressive therapy can significantly reduce these outbreaks and is likely safe during pregnancy.

Is Zelitrex safe during breasfeeding?

Zelitrex is approved for use during pregnancy. A small amount of oral valacyclovir will pass to baby during breastfeeding, but the American Academy of Pediatrics supports use of the drug while breastfeeding as no side effects have been reported.

Is it safe to take Zelitrex with alcohol?

Experts say that alcohol doesn’t affect the way Zelitrex works. Alcohol warnings aren’t listed on antiviral drugs like Zelitrex.

How quickly does Zelitrex work?

Zelitrex takes effect very quickly and provides some level of relief in as little as two to three days. Generally, the sooner you take Zelitrex after noticing symptoms, the faster it will be to provide relief.

Does Zelitrex make tired?

Zelitrex oral tablet doesn't cause drowsiness or tiredness, but it can cause other side effects.

How many Zelitrex can I take a day?

Zelitrex is usually not more than 1000 mg three times a day.The usual Zelitrex is 20 milligrams (mg) per kilogram (kg) of body weight, taken three times a day for 5 days.

Does Zelitrex raise blood pressure?

band may increased heart rate, and high blood pressure (hypertension).

Is long term use of Zelitrex safe?

Zelitrex may not safe taken long term, particularly in people with existing kidney issues and/or inadequate hydration, Zelitrex can lead to renal toxicity and kidney failure.

What happens if I take Zelitrex everyday?

Zelitrex taken daily reduces the number of outbreaks a person experiences and the number of days that someone sheds the virus asymptomatically.

Can I drink coffee while taking Zelitrex?

It is okay to take them unless told otherwise by a medical professional.When it comes to caffeine and Tylenol, two of the things most likely to be consumed while on Zelitrex.

Is Zelitrex antibiotic?

Zelitrex is an antiviral drug. It slows the growth and spread of the herpes virus to help the body fight the infection.

What should I avoid while taking Zelitrex?

Avoid sexual intercourse or use a latex condom to help keep you from spreading the herpes virus to others. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes.

Does Zelitrex interaction with other drugs?

Zelitrex has no known severe interactions with other drugs.

Why do I have to drink a lot of water while taking Zelitrex?

Drink extra fluids so you will pass more urine while you are using this medicine. This will keep your kidneys working well and help prevent kidney problems.

Does bnrand make my gain weight?

Weight changes are not commonly reported with the use of Zelitrex.

Do I have to take Zelitrex everyday for the rest of life?

To help clear up your infection, keep taking Zelitrex for the full time of treatment, even if your symptoms begin to clear up after a few days. Do not miss any doses.Do not use this medicine more often or for a longer time than your doctor ordered.

Can Zelitrex cause joint pain?

Zelitrex can causes Joint pain with other important side effects.

Is Zelitrex bad for my liver?

Zelitrex is not considered a liver toxic drug.When taken at a normal dose Zelitrex is highly unlikely to cause liver damage in individuals with normal liver health.

*** Taking medicines without doctor's advice can cause long-term problems.
Share