Aciclovir is a synthetic purine nucleoside analogue. It is mainly used for various infections caused by herpes simplex virus and can be used for primary or recurrent skin, mucous membrane, external genital infections and herpes simplex virus infections occurring in immunodeficient individuals. The antiviral mechanism of this product is that acyclovir enters the infected cells and is firstly converted into monophosphate by virus-specific thymidine kinase, then further converted into diphosphate and triphosphate compounds by the cell’s nucleoside kinase, and finally mimics the binding of nucleotides to viral polymorphic enzymes, adulterates viral DNA and aborts its extension, thus achieving the antiviral effect. Acyclovir is available in several dosage forms, including oral tablets, eye drops, creams, and gels. Acyclovir treatment is used to treat herpes simplex virus infections, herpes zoster, and varicella in immunodeficient individuals. 1, herpes simplex virus infection: oral use for initial and recurrent cases of facial and genital herpes virus infection; for recurrent cases oral use of the product as a prophylactic, also used for herpes simplex encephalitis treatment. 2.Herpes zoster: orally used for the treatment of cases of herpes zoster in immunocompetent persons and mild cases of herpes zoster in immunodeficient persons. 3.Treatment of varicella in immunodeficient persons.