Pharmacokinetics of intravenously and orally administered pyrimethamine in horses.
Single-dose pharmacokinetic variables of pyrimethamine were studied in horses. Pyrimethamine (1 mg/kg of body weight) was administered IV and orally to 6 adult horses, and plasma samples were obtained at frequent intervals thereafter. Plasma pyrimethamine concentration was assayed by gas chromatography, and concentration-time data were analyzed, using a pharmacokinetic computer program. The IV and oral administration data were best described by 3-compartment and 1-compartment models, respectively. The median volume of distribution at steady state after IV administration was 1,521 ml/kg and the median elimination half-time was 12.06 hours. Mean plasma concentration after oral administration fluctuated between a maximal concentration of 0.18 microgram/ml and 0.09 microgram/ml (24 hours after dosing). Bioavailability after oral administration was 56%.
Clarke
C R
CR
Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater 74078.
Burrows
G E
GE
MacAllister
C G
CG
Spillers
D K
DK
Ewing
P
P
Lauer
A K
AK
D000284:Administration, Oral; D000818:Animals; D002849:Chromatography, Gas / Q000662:veterinary; D005260:Female; D006736:Horses / Q000378:metabolism*; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male; D008954:Models, Biological; D011739:Pyrimethamine / Q000097:blood / Q000493:pharmacokinetics*
D011739:Pyrimethamine