Virostatic formulation containing acyclovir active ingredient. Acyclovir is a synthetic substance similar in structure to the guanine (component of nucleic acids complementary to cytosine) by reaction with the specific enzymes are transformed acyclovir in a pharmacologically active substance. In cells infected with viruses, produced by specific enzyme - thymidine kinase, which is by several chemical reactions convert acyclovir into acyclovir triphosphate. Due to saturation of the cytoplasm of the infected cell is a violation of acyclovir triphosphate DNA virus replication, resulting in the disruption of normal viral replication and the formation of non-viable viral units. The mechanism of drug action based on its structural similarity with deoxyguanosine triphosphate, whereby a competitive substitution occurs at nucleotide triphosphate of acyclovir in the synthesis of viral DNA. The drug has no effect on healthy cells, because they lack the enzyme thymidine kinase and acyclovir remains in an inactive form. Furthermore, the concentration of acyclovir in the infected cells is significantly higher than in healthy subjects. The drug exhibits virostatic activity against herpes simplex virus type I and II, the virus that causes chicken pox. Acyclovir is a relatively moderately active cytomegalovirus.
Prolonged use of the drug, particularly for patients suffering from immunodeficiency viruses development of resistance was observed for formulations containing acyclovir. Resistant virus strains are characterized by low or disorder thymidine structure, changes in the structure of the viral DNA polymerase.
When applied in the form of the drug acyclovir ophthalmic ointment is rapidly absorbed across the cornea and creates a high concentration in the aqueous humor. Systemic absorption of the drug when applied to the cornea negligible, almost determined acyclovir in plasma, a determined amount of acyclovir in urine.
In applying the drug in the form of ointments negligible systemic absorption of acyclovir.
For intravenous infusion, the maximum drug concentration in plasma was observed after 1 hour after infusion. The half-life in adults is 2.9 hours, 3.8 hours in the newborn.
After oral administration of the drug active ingredient is partially absorbed into the bloodstream. Before the drug at a dose of 200 mg every 4 hours maximum equilibrium concentration of drug in the blood plasma is about 3,1mkmol and minimum equilibrium concentration of the drug is about 1.8.
The degree of plasma protein due to low (from 9 to 33%). The drug in high concentrations in the cerebrospinal fluid is determined. Acyclovir is partially metabolized in the liver. Excreted mainly by the kidneys as intact or in the form of metabolites.
Older people have somewhat increased the half-life of acyclovir.
In patients worldwide, including the UK suffering from renal failure the half-life of acyclovir up to 19.5 hours, hemodialysis reduced to a half-life of 5.7 hours.
Indications established by experts from the UK
The product is intended for topical and systemic use in patients in the UK with such diseases:
- Infectious diseases of skin and mucosa caused by the herpes virus type I and II, including those for the treatment of primary genital herpes recurrence and;
- Infections caused by varicella-zoster virus and herpes zoster;
- Herpes infection I and type II in infants;
- The drug is also used for the prevention of infectious diseases caused by the herpes simplex virus, in patients suffering from immune deficiency;
- For the prevention of cytomegalovirus infection in operations for bone marrow transplantation.