Plasma disposition and fecal elimination of doramectin after oral or intramuscular administration in horses.
A study was done to compare plasma disposition kinetics and the fecal elimination profile of doramectin (DRM) after oral or intramuscular (IM) administration in horses. Ten clinically healthy horses, 328-502 kg body weight (bw), were assigned to 2 experimental groups of 5 horses each. Group 1 was treated with an oral dose of 0.2 mg DRM/kg bw, while Group 2 was treated with 0.2 mg DRM/kg bw by IM route. Blood and fecal samples were collected at different times between 0.5h and 60 days post-treatment. After plasma and fecal drug extraction and derivatization, samples were analysed by high performance liquid chromatography (HPLC). A non-compartmental kinetic analysis was performed. Results were expressed as mean+/-standard deviation and were compared using Mann-Whitney U-test. The parent molecule was detected in plasma between 30 min and either 30 (oral) or 60 (IM) days post-treatment. Peak plasma concentrations (C(max)) of 51.6+/-22.2 and 33.3+/-10.5 ng/mL were obtained after oral administration and IM route, respectively. Differences between administration route were not statistically significant (P=0.42). The value for the area under the concentration-time curve (AUC) was 178.6+/-53.7 and 393.6+/-66.6 ng day/mL for Group 1 and Group 2, respectively. These differences were significant (P<0.0079). The averages for mean residence time (MRT) values were 7.7+/-0.9 and 13.2+/-4.5 days for oral and IM treated groups, respectively. In horses treated using the oral route, the peak fecal concentration (F C max) was 2295+/-593 ng/g observed at 1.9+/-0.5 days after oral treatment. Whereas, for those treated by IM route, the F C max was lower (162+/-26 ng/g) (P<0.0079) and it was observed at 5.6+/-2.9 days. The results of this study showed that the administration route affects plasma disposition kinetics, bioavailability and fecal elimination of DRM.
Pérez
R
R
Facultad de Medicina Veterinaria, Universidad de Concepción, Chillán, Chile. rubperez@udec.cl
Godoy
C
C
Palma
C
C
Muñoz
L
L
Arboix
M
M
Alvinerie
M
M
D000284:Administration, Oral; D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D005243:Feces / Q000737:chemistry / Q000469:parasitology; D005260:Female; D006207:Half-Life; D006736:Horses / Q000378:metabolism* / Q000469:parasitology; D007273:Injections, Intramuscular / Q000662:veterinary; D007559:Ivermectin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D008297:Male; D010270:Parasite Egg Count / Q000662:veterinary
D000871:Anthelmintics; D007559:Ivermectin; C084101:doramectin