title: Bioavailability of oral penicillins in the horse: a comparison of pivampicillin and amoxicillin.
abstract: The pharmacokinetics of ampicillin and amoxicillin following intravenous administration at a dose rate of 15 and 10 mg/kg respectively were studied in four healthy adult horses. Pharmacokinetics of pivampicillin and amoxicillin were studied after oral administration to four healthy adult horses. Pivampicillin, a prodrug of ampicillin, was administered orally to starved and fed horses at a dose rate of 19.9 mg/kg, which is equivalent on a molecular basis to 15 mg/kg ampicillin. Amoxicillin was administered orally to starved horses only, at a dose rate of 20 mg/kg. Ampicillin and amoxicillin concentrations in plasma, synovial fluid and urine were determined. Mean biological half-life of intravenously administered ampicillin and amoxicillin was 1.72 and 1.43 h respectively, whilst the distribution volume (Vss) appeared to be 0.180 and 0.192 1/kg. Orally administered pivampicillin and amoxicillin were rapidly absorbed. A maximum concentration in plasma of 3.80 micrograms/ml was reached 2 h after administration of pivampicillin to starved horses; in fed horses a maximum concentration of 5.12 micrograms/ml was reached 1 h after administration. After oral administration of amoxicillin a maximum concentration of 2.03 micrograms/ml was reached after 1 h. The (absolute) bioavailability of pivampicillin administered orally was 30.9% in starved horses and 35.9% in fed horses. The bioavailability of amoxicillin administered orally was 5.3% in starved horses.
authors.affiliation: Department of General and Large Animal Surgery, State University of Utrecht, The Netherlands.
authors.forename: J M
authors.initials: JM
authors.lastname: Ensink
authors.forename: W R
authors.initials: WR
authors.lastname: Klein
authors.forename: D J
authors.initials: DJ
authors.lastname: Mevius
authors.forename: A
authors.initials: A
authors.lastname: Klarenbeek
authors.forename: A G
authors.initials: AG
authors.lastname: Vulto
mesh_terms: D000284:Administration, Oral; D000658:Amoxicillin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000667:Ampicillin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000818:Animals; D001682:Biological Availability; D005215:Fasting; D005260:Female; D006207:Half-Life; D006736:Horses / Q000378:metabolism*; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male; D010917:Pivampicillin / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D010917:Pivampicillin; D000667:Ampicillin; D000658:Amoxicillin