盐酸缬更昔洛韦片有耐药性吗？

It is the L-valyl ester (prodrug) of ganciclovir. After oral administration, it is rapidly converted into ganciclovir by esterases in the small intestine and liver.

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. 

Ganciclovir inhibits viral activity mainly by inhibiting viral DNA synthesis:

(a) Competitively inhibits viral DNA polymerase so that deoxyguanosine triphosphate cannot bind to DNA.

(b) Ganciclovir triphosphate binds to viral DNA to terminate or limit the elongation of the DNA chain. The IC50 (concentration of the inhibitor at which the "response" is inhibited by half) of the antiviral effect of ganciclovir on cytomegalovirus (CMV) in vitro ranges from 0.14μM (0.04ug/ml) to 14μM (3.5ug/ml). 

The U.S. Food and Drug Administration (FDA) has approved the increased use of valamciclovir hydrochloride in adult kidney transplant patients at high risk for cytomegalovirus (CMV) disease. 

Many patients will ask, will long-term use of valganciclovir hydrochloride tablets cause drug resistance?

Since each patient's constitution and disease progression are different, the time and manifestation of drug resistance are also different for each patient. When a patient develops drug resistance, he should consult the relevant doctor as soon as possible to change or replace the treatment plan.