Zelitrex

Zelitrex - General Information

Zelitrex (INN) or valacyclovir (USAN) is an antiviral drug used in the management of herpes simplex and herpes zoster (shingles). It is a prodrug, being converted in vivo to aciclovir. It is marketed by GlaxoSmithKline under the trade name Valtrex or Zelitrex. [Wikipedia]

 

Pharmacology of Zelitrex

Zelitrex (INN) or Valacyclovir (USAN) is a prodrug and synthetic purine nucleoside analogue with inhibitory activity against herpes simplex virus types 1 (HSV-1), 2 (HSV-2), varicella-zoster virus (VZV), Epstein-Barr virus (EBV), and cytomegalovirus (CMV). Zelitrex is almost completely converted to acyclovir and L-valine. The inhibitory activity of valaciclovir is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV and VZV. This viral enzyme converts acyclovir into acyclovir monophosphate, which is then converted into acyclovir diphosphate and triphosphate by cellular enzymes. Acyclovir is selectively converted to the active triphosphate form by cells infected with herpes viruses.

 

Zelitrex for patients

VALTREX (VAL-trex)

(valacyclovir hydrochloride) Caplets

Read the Patient Information that comes with VALTREX before you start using it and each time you get a refill. There may be new information. This information does not take the place of talking to your healthcare provider about your medical condition or treatment. Ask your healthcare provider or pharmacist if you have questions.

What is VALTREX?

VALTREX is a prescription antiviral medicine. VALTREX lowers the ability of herpes viruses to multiply in your body.

VALTREX is used:

· to treat cold sores (also called fever blisters or herpes labialis) in adults to treat shingles (also called herpes zoster) in adults

· to treat or control genital herpes outbreaks in adults with normal immune systems

· to control genital herpes outbreaks in adults infected with the human immunodeficiency virus (HIV) with CD4 cell count greater than 100 cells/mm³

· with safer sex practices to lower the chances of spreading genital herpes to others. Even with safer sex practices, it is still possible to spread genital herpes.

VALTREX used daily with the following safer sex practices can lower the chances of passing genital herpes to your partner.

· Do not have sexual contact with your partner when you have any symptom or outbreak of genital herpes.

· Use a condom made of latex or polyurethane whenever you have sexual contact.

VALTREX does not cure herpes infections (cold sores, shingles, or genital herpes).

VALTREX has not been studied in children who have not reached puberty.

What are cold sores, shingles, and genital herpes?

Cold sores are caused by a herpes virus that may be spread by kissing or other physical contact with the infected area of the skin. They are small, painful ulcers that you get in or around your mouth. It is not known if VALTREX can stop the spread of cold sores to others.

Shingles is caused by the same herpes virus that causes chickenpox. It causes small, painful blisters that happen on a certain area of your skin. Shingles occurs in people who have already had chickenpox. Shingles can be spread to people who have not had chickenpox or the chickenpox vaccine by contact with the infected areas of the skin. It is not known if VALTREX can stop the spread of shingles to others.

Genital herpes is a sexually transmitted disease. It causes small, painful blisters on your genital area. You can spread genital herpes to others, even when you have no symptoms. If you are sexually active, you can still pass herpes to your partner, even if you are taking VALTREX. VALTREX, taken every day as prescribed and used with the following safer sex practices, can lower the chances of passing genital herpes to your partner.

· Do not have sexual contact with your partner when you have any symptom or outbreak of genital herpes.

· Use a condom made of latex or polyurethane whenever you have sexual contact. Ask your healthcare provider for more information about safer sex practices.

Who should not take VALTREX?

Do not take VALTREX if you are allergic to any of its ingredients or to acyclovir. The active ingredient is valacyclovir. See the end of this leaflet for a complete list of ingredients in VALTREX.

Before taking VALTREX, tell your healthcare provider:

About all your medical conditions, including:

· if you have had a bone marrow transplant or kidney transplant, or if you have advanced HIV disease or "AIDS". Patients with these conditions may have a higher chance for getting a blood disorder called thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS). TTP/HUS can result in death.

· if you have kidney problems. Patients with kidney problems may have a higher chance for getting side effects or more kidney problems with VALTREX. Your healthcare provider may give you a lower dose of VALTREX.

· if you are 65 years of age or older. Elderly patients have a higher chance of certain side effects. Also, elderly patients are more likely to have kidney problems. Your healthcare provider may give you a lower dose of VALTREX.

· if you are pregnant or planning to become pregnant. Talk with your healthcare provider about the risks and benefits of taking prescription drugs (including VALTREX) during pregnancy.

· if you are breastfeeding. VALTREX may pass into your milk and it may harm your baby. Talk with your healthcare provider about the best way to feed your baby if you are taking VALTREX.

· about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. VALTREX may affect other medicines, and other medicines may affect VALTREX. This may happen if you have certain medical conditions such as kidney problems. It is a good idea to keep a complete list of all the medicines you take. Show this list to your healthcare provider and pharmacist any time you get a new medicine.

How should I take VALTREX?

Take VALTREX exactly as prescribed by your healthcare provider. Your dose of VALTREX and length of treatment will depend on the type of herpes infection that you have and any other medical problems that you have.

· Do not stop VALTREX or change your treatment without talking to your healthcare provider.

· VALTREX can be taken with or without food.

· If you are taking VALTREX to treat cold sores, shingles, or genital herpes, you should start treatment as soon as possible after your symptoms start. VALTREX may not help you if you start treatment too late.

· If you miss a dose of VALTREX, take it as soon as you remember and then take your next dose at its regular time. However, if it is almost time for your next dose, do not take the missed dose. Wait and take the next dose at the regular time.

· Do not take more than the prescribed number of VALTREX Caplets each day. Call your healthcare provider right away if you take too much VALTREX.

What are the possible side effects of VALTREX?

Kidney failure and nervous system problems are not common, but can be serious in some patients taking VALTREX. Nervous system problems include aggressive behavior, unsteady movement, shaky movements, confusion, speech problems, hallucinations (seeing or hearing things that are really not there), seizures, and coma. Kidney failure and nervous system problems have happened in patients who already have kidney disease and in elderly patients whose kidneys do not work well due to age. Always tell your healthcare provider if you have kidney problems before taking VALTREX. Call your doctor right away if you get a nervous system problem while you are taking VALTREX.

Common side effects of VALTREX include headache, nausea, stomach pain, vomiting, and dizziness. Side effects in HIV-infected adults include headache, tiredness, and rash. These side effects are usually mild and usually do not cause patients to stop taking VALTREX.

Other less common side effects include painful periods in women, joint pain, depression, low blood cell counts, and changes in tests that measure how well the liver and kidneys work.

Talk to your healthcare provider if you develop any side effects that concern you.

These are not all the side effects of VALTREX. For more information ask your healthcare provider or pharmacist.

How should I store VALTREX?

· Store VALTREX at room temperature, 59° to 77°F (15° to 25°C).

· Keep VALTREX in a tightly closed container.

· Do not keep medicine that is out of date or that you no longer need.

· Keep VALTREX and all medicines out of the reach of children.

General information about VALTREX

Medicines are sometimes prescribed for conditions that are not mentioned in patient information leaflets. Do not use VALTREX for a condition for which it was not prescribed. Do not give VALTREX to other people, even if they have the same symptoms you have. It may harm them.

This leaflet summarizes the most important information about VALTREX. If you would like more information, talk with your healthcare provider. You can ask your healthcare provider or pharmacist for information about VALTREX that is written for health professionals. More information is available at www.VALTREX.com.

What are the ingredients in VALTREX?

Active Ingredient: valacyclovir hydrochloride

Inactive Ingredients: carnauba wax, colloidal silicon dioxide, crospovidone, FD&C Blue No. 2 Lake, hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polysorbate 80, povidone, and titanium dioxide.

 

Zelitrex Interactions

The pharmacokinetics of digoxin was not affected by coadministration of Valacyclovir 1 gram 3 times daily, and the pharmacokinetics of acyclovir after a single dose of Valacyclovir (1 gram) was unchanged by coadministration of digoxin (2 doses of 0.75 mg), single doses of antacids (Al3+ or Mg++), or multiple doses of thiazide diuretics. Acyclovir Cmax and AUC following a single dose of Valacyclovir (1 gram) increased by 8% and 32%, respectively, after a single dose of cimetidine (800 mg), or by 22% and 49%, respectively, after probenecid (1 gram), or by 30% and 78%, respectively, after a combination of cimetidine and probenecid, primarily due to a reduction in renal clearance of acyclovir. These effects are not considered to be of clinical significance in subjects with normal renal function. Therefore, no dosage adjustment is recommended when Valacyclovir is coadministered with digoxin, antacids, thiazide diuretics, cimetidine, or probenecid in subjects with normal renal function.

 

Zelitrex Contraindications

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

 

Additional information about Zelitrex

Zelitrex Indication: For the treatment or suppression of cold sores (herpes labialis), herpes zoster (shingles), genital herpes in immunocompetent individuals, and recurrent genital herpes in HIV-infected individuals.
Mechanism Of Action: Zelitrex is phosphorylated by viral thymidine kinase to acyclovir triphosphate (the active metabolite) which then inhibits herpes viral DNA replication by competitive inhibition of viral DNA polymerase, and by incorporation into and termination of the growing viral DNA chain. When used as a substrate for viral DNA polymerase, acyclovir triphosphate competitively inhibits dATP leading to the formation of 'faulty' DNA. This is where acyclovir triphosphate is incorporated into the DNA strand replacing many of the adenosine bases. This results in the prevention of DNA synthesis, as phosphodiester bridges can longer to be built, destabilizing the strand.
Drug Interactions: Not Available
Food Interactions: Not Available
Generic Name: Valaciclovir
Synonyms: Valaciclovir Hcl; Valaciclovir Hydrochloride; Valacyclover Hydrochloric; Valacyclover Hydrochloride; Valacyclovir Hydrochloride; Valacyclovir
Drug Category: Prodrugs; Antiviral Agents
Drug Type: Small Molecule; Approved; Investigational

Other Brand Names containing Valaciclovir: Valtrex; Zelitrex;
Absorption: After oral administration, valaciclovir hydrochloride is rapidly absorbed from the gastrointestinal tract. The absolute bioavailability of acyclovir after administration of valaciclovir is 54.5% ± 9.1%.
Toxicity (Overdose): Adverse effects of overexposure might include headache and nausea.
Protein Binding: 13-18%
Biotransformation: Valaciclovir is rapidly and almost entirely (~99%) converted to the active compound, acyclovir, and L-valine by first-pass intestinal and hepatic metabolism by enzymatic hydrolysis. Neither valaciclovir nor acyclovir is metabolized by cytochrome P450 enzymes.
Half Life: 2.5-3.3 hours
Dosage Forms of Zelitrex: Tablet Oral
Chemical IUPAC Name: 2-[(2-amino-6-oxo-3H-purin-9-yl)methoxy]ethyl (2S)-2-amino-3-methylbutanoate
Chemical Formula: C13H20N6O4
Valaciclovir on Wikipedia: https://en.wikipedia.org/wiki/Valaciclovir
Organisms Affected: Human Herpes Virus