Valacyclovir is an antiviral agent, it is an L-valine ester of acyclovir. Acyclovir is an analogue of a purine nucleoside (guanine).
In the human body, valacyclovir is rapidly and completely converted into acyclovir and valine under the action of the enzyme valacyclovirhydrolase. Acyclovir inhibits the synthesis of viral DNA immediately after phosphorylation and conversion into an active form - acyclovir triphosphate. The first stage of phosphorylation requires the activity of virus-specific enzymes. Activation of acyclovir with a specific viral enzyme largely explains its selectivity.
The process of phosphorylation of acyclovir (conversion from mono- to triphosphate) is completed by cellular kinases. Acyclovirrythophosphate competitively inhibits viral DNA polymerase and, being an analogue of the nucleoside, is inserted into viral DNA, which leads to obligatory rupture of the chain, termination of DNA synthesis and, consequently, blocking of viral replication.
Resistance is usually due to a deficiency of thymidine kinase, which leads to excessive spread of the virus in the host organism. Sometimes a decrease in sensitivity to acyclovir is due to the appearance of strains of the virus with a violation of the structure of the viral thymidine kinase or DNA polymerase. The virulence of these varieties of the virus resembles that of its wild strain.
- treatment of herpes zoster (Herpes zoster) (drug contributes to the relief of pain, reduces its duration and the percentage of patients with pain caused by herpes zoster, including acute and postherpetic neuralgia);
- treatment of infections of the skin and mucous membranes caused by HSV, including the newly identified and recurring genital herpes (Herpes genitalis), as well as labial herpes (Herpes labialis);
- prevention (suppression) of recurrences of infections of the skin and mucous membranes caused by HSV, including genital herpes;
- prevent the transmission of genital herpes to a healthy partner when taken as a suppressive therapy in conjunction with safe sex.
Adults and teenagers from 12 years and older:
- prevention of CMV infection, as well as reactions of acute graft rejection (in patients with kidney transplants), opportunistic infections and other herpes-viral infections (HSV, VZV) after organ transplantation.
- hypersensitivity to valaciclovir, acyclovir or any other component of the drug;
- children under 12 years old in the prevention of CMV infection after transplantation;
- children under 18 years of age for all other indications (due to the lack of data on clinical studies for this age group).
With caution: patients with renal insufficiency; patients with clinically expressed forms of HIV infection; concurrent administration of nephrotoxic drugs.