title: Rifampin disposition in the horse: effects of age and method of oral administration.
abstract: The effects of time and method of administration of rifampin with respect to feeding were evaluated in five mature horses. There was a significant (P less than or equal to 0.05) delay in time of maximum serum concentration and an apparent but not significant decrease in oral absorption when rifampin was given as a top dressing on grain as compared with administration in corn syrup 2 h before or 2 h after feeding. Although there were no differences between administration before or after feeding, administration 2 h prior to feeding was selected as the method of choice for future experiments. The effects of age on rifampin disposition were subsequently examined using this method of administration in six, 1-week old foals. Rifampin (10 mg/kg) was given at increasing age from 1 through 10 weeks and the pharmacokinetic disposition parameters compared. There were significant differences in the slope of the elimination phase (beta) and area under the curve (AUC) at 1 week through 6 weeks compared with 10 weeks or with values in the five mature horses.
authors.affiliation: Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater 74078-0353.
authors.forename: G E
authors.initials: GE
authors.lastname: Burrows
authors.forename: C G
authors.initials: CG
authors.lastname: MacAllister
authors.forename: P
authors.initials: P
authors.lastname: Ewing
authors.forename: E
authors.initials: E
authors.lastname: Stair
authors.forename: P W
authors.initials: PW
authors.lastname: Tripp
mesh_terms: D000284:Administration, Oral; D000375:Aging / Q000378:metabolism*; D000821:Animal Feed; D000818:Animals; D005260:Female; D006736:Horses / Q000378:metabolism*; D007408:Intestinal Absorption; D008297:Male; D012293:Rifampin / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D012293:Rifampin