title: Ganciclovir absolute bioavailability and steady-state pharmacokinetics after oral administration of two 3000-mg/d dosing regimens in human immunodeficiency virus- and cytomegalovirus-seropositive patients.
abstract: Oral ganciclovir has recently been approved for use in long-term maintenance therapy in the treatment of cytomegalovirus (CMV) retinitis in immunocompromised patients. Although oral ganciclovir at a dose of 3,000 mg/d is moderately less effective than intravenous (i.v.) ganciclovir maintenance therapy (5 mg/kg as a 1-hour i.v. infusion every 24 hours), convenience and practicality make oral maintenance therapy desirable. Two dosing regimens--1,000 mg three times daily (TID) and 500 mg every 3 hours (six times daily)--have been shown to be efficacious. Eighteen human immunodeficiency virus- and CMV-seropositive patients participated in a three-way, open-label, crossover study to evaluate the steady-state pharmacokinetics and absolute bioavailability of the two oral regimens compared with the i.v. regimen. Sixteen patients completed the study and received ganciclovir as a single 5-mg/kg i.v. infusion over 1 hour, 500 mg orally every 3 hours while awake (six times daily) for 3 days, and 1,000 mg TID orally for 3 days. Blood samples were obtained over a 24-hour period after the single i.v. dose and on day 3 of the oral dosing regimens. Mean peak serum concentrations were 8.27, 1.02, and 1.18 micrograms/mL for the i.v. and oral regimens, respectively. Twenty-four-hour area under the curve (AUC) for the oral regimens--500 mg every 3 hours and 1,000 mg TID--were 15.9 and 15.4 micrograms.h/mL, respectively, as compared with a total AUC of 22.1 micrograms.h/mL for the single i.v. dose. The absolute bioavailabilities for the two oral regimens were 8.84% and 8.53%, respectively. The extent of ganciclovir absorption, peak concentrations, and average concentration at steady state were not statistically different between the two oral regimens. The peak-to-trough concentration ratio (Cmax:Cmin) was greater for the 1,000-mg TID regimen than for the regimen of 500 mg every 3 hours (5.35 vs 3.81 [P < 0.01]). Both oral regimens resulted in concentrations in the range of the concentration that inhibits 50% of most human CMV isolates. Because both oral regimens provide equivalent absorption, the 1,000-mg TID regimen may be preferred for the convenience and potentially greater compliance associated with fewer daily doses.
authors.affiliation: Novum, Inc., Pittsburgh, Pennsylvania, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Anderson
authors.forename: K G
authors.initials: KG
authors.lastname: Griffy
authors.forename: D
authors.initials: D
authors.lastname: Jung
authors.forename: A
authors.initials: A
authors.lastname: Dorr
authors.forename: J D
authors.initials: JD
authors.lastname: Hulse
authors.forename: R B
authors.initials: RB
authors.lastname: Smith
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000998:Antiviral Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001682:Biological Availability; D018592:Cross-Over Studies; D003586:Cytomegalovirus Infections / Q000378:metabolism*; D005260:Female; D015774:Ganciclovir / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006679:HIV Seropositivity / Q000378:metabolism*; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male
chemical_list: D000998:Antiviral Agents; D015774:Ganciclovir