Ganciclovir
Ganciclovir is an analog of acyclovir and is the first antiviral agent approved for the treatment of cytomegalovirus (CMV) infection. It is widely used for the treatment of CMV infections among patients with impaired cell-mediated immunity such as HIV/AIDS and recipients of solid organ and bone marrow transplantation who are at high risk for invasive CMV disease.
Valcyte (valganciclovir) is an oral prodrug of ganciclovir ester that is converted to ganciclovir in the bloodstream. The oral dose is designed to deliver ganciclovir equivalent to intravenous ganciclovir at 5 mg/kg.
Ganciclovir is converted to ganciclovir triphosphate, which is a competitive inhibitor of deoxyguanosine triphosphate. Incorporation of ganciclovir triphosphate into DNA inhibits viral DNA polymerases more than cellular DNA polymerases and disrupts viral DNA synthesis. The circulating half-life is two to four hours. Ganciclovir is excreted unmodified in the urine.
Both ganciclovir and valganciclovir are associated with bone marrow suppression, especially leukopenia. Monitoring of ganciclovir serum concentrations is most useful in guiding therapy of patients with renal dysfunction. Serum creatinine and complete blood count should be checked at least weekly during induction therapy and at least monthly during maintenance therapy.
Therapeutic ranges have not been well-established for ganciclovir. They are based on typical values seen during ganciclovir therapy and do not correlate well to toxicity or outcome.
Reference Values using HPLC for quantitation are:
Trough: 1.0-3.0 ug/mL
Peak: 3.0-12.5 ug/mL
Serum for a peak level should be drawn 30 to 60 minutes after dosing. Serum for a trough level should be drawn no more than 30 minutes before the next dose.
Specimen requirement is a plain red top tube of blood without gel.
