title: Pharmacokinetics and metabolism of rimantadine hydrochloride in mice and dogs.
abstract: We studied the pharmacokinetics and metabolism of rimantadine hydrochloride (rimantadine) following single-dose oral and intravenous administration in mice and dogs. Absorption of the compound in mice was rapid. Maximum concentrations in plasma occurred at less than 0.5 h after oral administration, and the elimination half-life was 1.5 h. Peak concentrations in plasma following oral administration were markedly disproportional to the dose (274 ng/ml at 10 mg/kg, but 2,013 ng/ml at 40 mg/kg). The bioavailability after an oral dose of 40 mg/kg was 58.6%. Clearance was 4.3 liters/h per kg, and the volume of distribution was 7.6 liters/kg at 40 mg/kg. In contrast to the results observed in mice, absorption of the compound in dogs was slow. Maximum concentrations in plasma occurred at 1.7 h after oral administration, and the elimination half-life was 3.3 h. A further difference was that peak concentrations in plasma were approximately proportional to the dose. Following administration of a single oral dose of 5, 10, or 20 mg/kg, maximum concentrations in plasma were 275,800, and 1,950 ng/ml, respectively. The bioavailability after an oral dose of 5 mg/kg was 99.4%. The clearance was 3.7 liters/h per kg, and the volume of distribution was 13.8 liters/kg at 5 mg/kg. Mass balance studies in mice, using [methyl-14C]rimantadine, indicated that 98.7% of the administered dose could be recovered in 96 h. Less than 5% of the dose was recovered as the parent drug in dog urine within 48 h. Finally, gas chromatography-mass spectrometry studies, done with mouse plasma, identified the presence of two rimantadine metabolites. These appeared to be ring-substituted isomers of hydroxy-rimantadine.
authors.affiliation: Medical Products Department, E.I. du Pont de Nemours & Co., Inc., Wilmington, Delaware 19898.
authors.forename: H E
authors.initials: HE
authors.lastname: Hoffman
authors.forename: J C
authors.initials: JC
authors.lastname: Gaylord
authors.forename: J W
authors.initials: JW
authors.lastname: Blasecki
authors.forename: L M
authors.initials: LM
authors.lastname: Shalaby
authors.forename: C C
authors.initials: CC
authors.lastname: Whitney
mesh_terms: D000218:Adamantane / Q000031:analogs & derivatives*; D000284:Administration, Oral; D000547:Amantadine / Q000378:metabolism; D000818:Animals; D001682:Biological Availability; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005243:Feces / Q000032:analysis; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D008168:Lung / Q000378:metabolism; D008657:Metabolic Clearance Rate; D051379:Mice; D009976:Orthomyxoviridae Infections / Q000378:metabolism; D012299:Rimantadine / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics*
chemical_list: D012299:Rimantadine; D000547:Amantadine; D000218:Adamantane