盐酸缬更昔洛韦片是什么药呢？

Valcyte is the L-valyl ester (prodrug) of ganciclovir, which is rapidly converted into ganciclovir by esterases in the small intestine and liver after oral administration. Ganciclovir is a synthetic analog of 2’-deoxyguanosine that inhibits herpes virus replication in vitro and in vivo. Susceptible human viruses include human cytomegalovirus (HCMV), herpes simplex virus-1 and herpes simplex virus-2 (HSV-1, HSV-2), human herpesvirus-6, 7, 8 (HHV-6, 7, 8), Epstein-Barr virus, varicella-zoster virus (VZV), and hepatitis B virus. In cells infected with cytomegalovirus (CMV), ganciclovir is first phosphorylated by the viral protein kinase UL97 to ganciclovir monophosphate. It is further phosphorylated by intracellular protein kinases into ganciclovir triphosphate, which is then slowly metabolized within the cell. After removal of extracellular ganciclovir, the half-life of ganciclovir in HSV- or HCMV-infected cells is 18 hours and 6 to 24 hours, respectively. Since phosphorylation is largely dependent on viral protein kinases, ganciclovir phosphorylation occurs preferentially in virus-infected cells. 

Valcyte hydrochloride tablets (valcyte) inhibits viral activity mainly by inhibiting the synthesis of viral DNA: (a) competitively inhibits viral DNA polymerase, preventing deoxyguanosine triphosphate from binding to DNA; (b) ganciclovir triphosphate binds to viral DNA to terminate or limit the elongation of the DNA chain. The IC50 of ganciclovir's antiviral effect on CMV in vitro ranges from 0.14μM (0.04ug/ml) to 14μM (3.5ug/ml).

In May 2001, it was approved by the US FDA for marketing. The tablet is clinically used to treat acute retinitis caused by CMV infection in patients with acquired immunodeficiency syndrome (AIDS). In May 2003, its indications were expanded to prevent and treat secondary CMV infection in organ transplant recipients.