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Vitrasert

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Vitrasert

Vitrasert

CLINICAL PHARMACOLOGY

Virology

Ganciclovir is a synthetic nucleoside analogue of 2'-deoxyguanosine that inhibits replication of herpes viruses both in vitro and in vivo. Sensitive human viruses include cytomegalovirus (CMV), herpes simplex virus -1 and -2 (HSV-1, HSV-2), Epstein-Barr virus (EBV) and varicella zoster virus (VZV). Clinical studies have been limited to assessment of efficacy in patients with CMV infection.

Median effective inhibitory doses (ED50) of ganciclovir for human CMV isolates tested in vitro in several cell lines ranged from 0.2 to 3.0 g/mL. The relationship between in vitrosensitivity of CMV to ganciclovir and clinical response has not been established. Ganciclovir inhibits mammalian cell proliferation in vitro at higher concentrations (10 to 60 g/mL) with bone marrow colony forming cells being the most sensitive (ID50 ≥ 10 g/mL) of those cell types tested.

Emergence of viral resistance has been reported based on in vitro sensitivity testing of CMV isolates from patients receiving intravenous ganciclovir treatment. The prevalence of resistant isolates is unknown, and there is a possibility that some patients may be infected with strains of CMV resistant to ganciclovir. Therefore, the possibility of viral resistance should be considered in patients who show poor clinical response.

Pharmacokinetics

In a clinical trial of Vitrasert (ganciclovir) Implants, 26 patients (30 eyes) received a total of 39 primary implants and 12 exchange implants (performed 32 weeks after the implant was inserted or earlier if progression of CMV retinitis occurred). Because most of the exchanged implants were empty, the time the implant actually ran out of drug was unknown, and a precise in-vivo release rate could not be calculated. However, approximate in-vivo release rates could be determined for the exchanged implants, which ranged from 1.00 g/h to more than 1.62 g/h.

In 14 implants (3 exchanged, 11 autopsy) in which the in-vivo release rate could accurately be calculated, the mean release rate was 1.40 g/h, with a range from 0.5 to 2.88 g/h. The mean vitreous drug levels in eight eyes (4 collected at the time of retinal detachment surgery; 2 collected from autopsy eyes within 6 hours of death and prior to fixation; 2 collected from implant exchanges) was 4.1 g/mL.

Last reviewed on RxList: 12/2/2008
This monograph has been modified to include the generic and brand name in many instances.

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