Valtrex, pills 500mg, 10pcs

Composition

Valacyclovir (L-valine ester of acyclovir) 500 mg

Pharmacological action

Pharmaceutical group:

antiviral agent.

Pharmaceutical effect:

Valtrex is an antiviral drug. In humans, valacyclovir is rapidly and completely converted to acyclovir by valacyclovir hydrolase.

Acyclovir in vitro has specific inhibitory activity against Herpes simplex viruses types 1 and 2, Varicella zoster and Epstein-Barr, cytomegalovirus and human herpes virus type 6.

Acyclovir inhibits viral DNA synthesis immediately after phosphorylation and conversion to the active form of acyclovir triphosphate. The first stage of phosphorylation occurs with the participation of virus-specific enzymes. For Herpes simplex, Varicella zoster, and Epstein-Barr viruses, such an enzyme is viral thymidine kinase, which is present in virus-affected cells. Partial phosphorylation selectivity is preserved in cytomegalovirus and is mediated through the phosphotransferase gene product UL 97. Activation of acyclovir by a specific viral enzyme greatly explains its selectivity.

The process of phosphorylation of acyclovir (conversion from mono – to triphosphate) is completed by cellular kinases. Acyclovir triphosphate competitively inhibits viral DNA polymerase and, being a nucleoside analog, is incorporated into viral DNA, which leads to an obligate (complete) chain break, stopping DNA synthesis and, consequently, blocking viral replication.

In immunocompromised patients, Herpes simplex and Varicella zoster viruses with reduced sensitivity to valacyclovir are extremely rare (less than 0.1%), but can sometimes be detected in patients with severe immune disorders, for example, with a bone marrow transplant, in those receiving chemotherapy for malignancies, and in HIV-infected patients.

Resistance is caused by a deficiency of thymidine kinase of the virus, which leads to excessive spread of the virus in the host. Sometimes a decrease in sensitivity to acyclovir is due to the appearance of virus strains with a violation of the structure of viral thymidine kinase or DNA polymerase. The virulence of these varieties of the virus is similar to that of its wild strain.

Pharmacokinetics:  

Valacyclovir and acyclovir have similar pharmacokinetic parameters after oral use.

Suction

After oral use, valacyclovir is well absorbed from the gastrointestinal tract, quickly and almost completely converted to acyclovir and valine. This transformation is catalyzed by the enzyme valacyclovir hydrolase, isolated from the human liver.

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 the median time to reach this concentration is 1-2 hours.

When taking valacyclovir at a dose of 1 g or more, the bioavailability of acyclovir is 54% and does not depend on food intake.

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

Distribution

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

Deduction

In patients with normal renal function, the T1/2 of acyclovir is approximately 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. Pharmacokinetics in special clinical cases

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

The pharmacokinetics of valacyclovir and acyclovir are largely unaffected in patients infected with Herpes simplex and Varicella zoster viruses.

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.

Taking Valtrex at a dose of 1 g and 2 g does not affect the distribution and pharmacokinetic parameters of valacyclovir in HIV-infected patients compared with healthy individuals.

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 the drug, and their daily AUC values are significantly higher.

Indications

– treatment of herpes zoster caused by the Varicella zoster virus (accelerates the disappearance of pain, reduces its duration and the percentage of patients with pain, including acute and postherpetic neuralgia);- treatment of skin and mucosal infections caused by Herpes simplex virus type 1 and 2 (including newly diagnosed and recurrent genital herpes);- treatment of labial herpes (labial fever);- Valtrex is able to prevent the formation of lesions, if it is taken at the first symptoms of a relapse of herpes simplex;- prevention (suppression) of recurrent diseases of the skin and mucous membranes caused by the Herpes simplex virus type 1 and 2, including genital herpes;- Valtrex can reduce genital herpes infection in a healthy partner if taken as a suppressive therapy in combination with safe sex;- prevention of cytomegalovirus infection that occurs during organ transplantation (reduces the severity of acute graft rejection in patients with kidney transplants, the development of opportunistic infections and other viral infections caused by Herpes simplex and Varicella zoster viruses).

Use during pregnancy and lactation

There are limited data on the use of Valtrex in pregnancy. Valtrex is used only in cases where the potential benefit to the mother exceeds the possible risk to the fetus.

Caution is recommended when prescribing Valtrex during lactation.

Contraindications

Hypersensitivity (including to acyclovir).

Side effects

Adverse reactions are listed below according to the classification by major systems and organs and by frequency of occurrence: very common (≥1/10), common (≥1/100, From the central nervous system: often-headache.

From the digestive system: often – nausea. Post-marketing research data

Immune system disorders: very rare-anaphylaxis.

From the central nervous system: rarely-dizziness, confusion, hallucinations, decreased mental abilities; very rarely-agitation, tremor, ataxia, dysarthria, psychotic symptoms, convulsions, encephalopathy, coma.

These reactions are reversible and usually occur in patients with impaired renal function or other predisposing conditions. In patients with organ transplants who receive Valtrex in high doses (8 g/day) for the prevention of cytomegalovirus infection, neurological reactions develop more often than when taking lower doses.

From the respiratory system: infrequently-dyspnoea.

From the digestive system: rarely-abdominal discomfort, vomiting, diarrhea; very rarely-reversible violations of liver function tests (which are sometimes regarded as manifestations of hepatitis).

From the hematopoietic system: very rarely – leukopenia (mainly observed in patients with reduced immunity), thrombocytopenia. Dermatological reactions: infrequently-rash, photosensitivity; rarely-pruritus.

Allergic reactions: very rarely – urticaria, angioedema.

From the urinary system: rarely-impaired renal function; very rarely-acute renal failure, renal colic (may be associated with impaired renal function).

Other services: Renal failure, microangiopathic hemolytic anemia, and thrombocytopenia (sometimes combined) have been reported in patients with severe immune disorders, especially late-stage AIDS, who receive valacyclovir in high doses (8 g/day daily) for a long time. Similar adverse reactions have been reported in patients with the same medical conditions but not treated with valacyclovir.

Interaction

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

Acyclovir is mainly excreted unchanged in the urine as a result of active tubular secretion. After taking Valtrex at a dose of 1 g, cimetidine and probenecid, which block tubular secretion, increase the AUC of acyclovir and reduce its renal clearance. However, no dose adjustment of Valtrex is required, as acyclovir has a broad therapeutic index.

Valtrex should be used with caution in higher doses (4 g/day) simultaneously with medications that compete with acyclovir for the elimination pathway, since there is a risk of increased plasma levels of one or both drugs or their metabolites.

There was an increase in the AUC of acyclovir and the inactive metabolite mycophenolate mofetil (an immunosuppressant used in transplantation) with simultaneous use of these drugs.

Caution should be exercised when combining Valtrex in a high dose (4 g / day). and above) with drugs that violate kidney function (including cyclosporine, tacrolimus).

How to take it, course of use and dosage

Inside. Adults with herpes zoster – 1000 mg 3 times a day (7 days).

For herpes simplex – 500 mg 2 times a day; for relapses-for 5 days.

In the first episode with a severe course, the duration of treatment can be increased to 10 days.

Overdose

Currently, there are insufficient data on Valtrex overdose.

Symptoms: with a single oral dose of acyclovir in an excessive dose of up to 20 g, partial absorption from the gastrointestinal tract occurred, which was not accompanied by a toxic effect of the drug.

Oral use of acyclovir in excessive doses for several days was accompanied by gastrointestinal (nausea, vomiting) and neurological symptoms (headache, confusion). Intravenous use of acyclovir in excessive doses was accompanied by an increase in serum creatinine levels and subsequent development of renal failure, with neurological complications including confusion, hallucinations, agitation, convulsions, and coma.

Treatment: Patients should be closely monitored for signs of toxic effects. Hemodialysis significantly enhances the removal of acyclovir from the blood and can be considered the method of choice in the management of patients with an overdose of Valtrex.

Special instructions

Patients at risk of dehydration, especially elderly patients, should be adequately hydrated during treatment with Valtrex.

Patients with renal insufficiency have an increased risk of developing neurological complications.

In patients with impaired liver function in patients with mild or moderate cirrhosis of the liver (synthetic liver function is preserved), no dose adjustment of Valtrex is required. The pharmacokinetic study in patients with severe cirrhosis of the liver (with impaired synthetic liver function and the presence of shunts between the portal system and the general vascular bed) also did not receive data indicating the need to adjust the dosage regimen; however, the clinical experience of using Valtrex in this category of patients is organic.

There are no data on the use of Valtrex in high doses (4 g/day or more) in patients with liver diseases, so caution should be exercised when prescribing the drug in high doses to this category of patients.

Elderly patients do not need to adjust the dose, except in cases of significant renal impairment. It is necessary to maintain an adequate water-electrolyte balance.

No specific studies have been conducted to investigate the effects of Valtrex in liver transplant patients. However, high-dose prophylactic use of acyclovir has been shown to reduce cytomegalovirus infection.

Valtrex suppressive therapy reduces the risk of transmission of genital herpes, but does not completely eliminate it and does not lead to a complete cure. During Valtrex therapy, the patient should take measures to ensure the safety of the partner during sexual contact.

Use in pediatrics

There is no experience of clinical use of the drug in children.

Influence on the ability to drive motor vehicles and work with mechanismspecial precautions are not required.

Form of production

Pills.

Storage conditions

At a temperature not exceeding 30 °C

Shelf life

3 years

Active ingredient

Valacyclovir

Conditions of release from pharmacies

By prescription

Dosage form

Tablets

Purpose

For adults by doctor’s prescription, Children by doctor’s prescription, Children over 12 years of age

Indications

Herpes, Cytomegalovirus infection