Broad-spectrum antiviral drug. It has the effect of inhibiting the growth of multiple viruses such as respiratory syncytial virus, influenza virus, hepatitis A virus, adenovirus, etc. in vitro, and its mechanism is not fully understood. After entering the virus-infected cells, the drug is rapidly phosphorylated, and its product acts as a competitive inhibitor of viral synthase, inhibiting inosine monophosphate dehydrogenase, influenza virus RNA polymerase and mRNA guanosine transferase, thereby causing a decrease in intracellular guanosine triphosphate, impairing viral RNA and protein synthesis, and inhibiting viral replication and transmission. It may also have an immune effect and neutralizing antibody effect on respiratory syncytial virus.

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It has analgesic, sedative, hypnotic and tranquilizing effects. Its analgesic effect is weaker than pethidine, but stronger than general antipyretic analgesics. It has no respiratory depression effect at therapeutic doses, nor does it cause gastrointestinal smooth muscle spasm. It has a better effect on chronic persistent pain and dull visceral pain, but has a poor effect on acute sharp pain (such as postoperative pain, traumatic pain, etc.) and advanced cancer pain. While producing analgesic effects, it can also cause sedation and hypnosis. The therapeutic dose is non-addictive.

This product is first converted into 5-fluoro-2-deoxyuridine nucleotide in the body, which inhibits thymine nucleotide synthetase, blocking the conversion of deoxyuridine nucleotide into deoxythymine nucleotide, thereby inhibiting DNA biosynthesis. In addition, by preventing uracil and orotic acid from incorporating into RNA, the effect of inhibiting RNA synthesis is achieved. This product is a cell cycle-specific drug that mainly inhibits S-phase cells.

This product is an antiviral drug. It has an inhibitory effect on herpes simplex virus, herpes zoster virus, cytomegalovirus, etc. in vitro. After entering the cells infected by herpes virus, this product competes with deoxynucleoside for viral thymidine kinase or cell kinase, and the drug is phosphorylated into activated acyclovir triphosphate, and then inhibits viral replication in two ways: ① Interfering with viral DNA polymerase and inhibiting viral replication; ② Under the action of DNA polymerase, it binds to the growing DNA chain, causing the extension of the DNA chain to be interrupted. This product has a special affinity for viruses, but has low toxicity to mammalian host cells.