In infected cells containing viral thymidine kinase, phosphorylation and conversion to acyclovir monophosphate occurs. Under the influence of guanylyl cyclase acyclovir monophosphate is converted into diphosphate and under the influence of several cellular enzymes – in triphosphate. High selectivity of action and low toxicity for humans are due to the lack of the necessary enzyme for the formation of acyclovir triphosphate in intact cells of the macroorganism.
Acyclovir triphosphate inhibits the synthesis (replication) of the virus DNA by three mechanisms:
1) competitively replaces deoxyguanosine triphosphate in DNA synthesis;
2) “embedded” in the synthesized DNA chain and stops its elongation;
3) inhibits the enzyme DNA polymerase of viruses. As a result, the reproduction of the virus in the human body is disrupted.
Precautions for the substance Acyclovir
In the treatment with acyclovir, a large amount of liquid is recommended (to prevent the formation of a precipitate of acyclovir in the renal tubules).
Care should be taken with IV administration to patients with neurological disorders, impaired liver function, electrolyte balance disorders, pronounced hypoxia, and with impaired renal function (and when administered internally). To reduce the risk of kidney damage with IV administration, the drug should be injected slowly, within 1 hour. When symptoms of nephropathy appear, the drug is canceled.
The toxic effect of acyclovir on the CNS is more likely in patients with impaired immunity, in elderly patients, using high doses.
In the treatment with acyclovir, thrombocytopenic purpura and / or hemolytic uremic syndrome, in rare cases with a fatal outcome, in patients with clinically expressed forms of HIV infection were recorded in clinical practice.
It is not recommended for prescribing to children for the treatment of chicken pox if the disease is mild.
In the treatment of genital herpes, sexual intercourse should be avoided or condoms should be used. The use of acyclovir does not prevent the transmission of the virus to the partner.
Cream and ointment for external use (5%) is not recommended to be applied to the mucous membranes of the mouth and eyes. Possibly the development of pronounced local inflammation.