Gastrointestinal parasitism reduces the plasma availability of doramectin in lambs.
A study was undertaken to investigate the effect of parasitism on plasma availability and pharmacokinetic behaviour of doramectin (DRM) in lambs. Fourteen parasitised grey face Suffolk lambs (26.9 +/- 1.5 kg bodyweight) were selected for the study. Seven pairs of lambs were allocated to two groups to obtain an approximately even weight distribution. Group I (non-parasitised) was pre-treated with three repeated administrations of 5 mg/kg fenbendazole to maintain a parasite free condition. In group II (parasitised), the lambs did not receive any anthelmintic treatment. After the 85-day pre-treatment period, both groups of animals were treated with DRM by subcutaneous (SC) injection in the shoulder area at 200 microg/kg. Throughout the experimental period, both groups were maintained together under similar feeding and management conditions. Blood samples were collected by jugular venepuncture at different set times between 0.5 h and 60 days post-treatment. After plasma extraction and derivatisation, samples were analysed by high performance liquid chromatography (HPLC) with fluorescence detection. A computerised kinetic analysis was performed and the data were compared using the Student's paired t test. The parent molecule was detected in plasma between 30 min and either day 20 (parasitised) or day 35 (non-parasitised) post-DRM treatment. The AUC values of the parasitised group (143.0 +/- 18 ng d/mL) were significantly lower (P<0.05) than those observed in the parasitically naïve animals (229.6 +/- 21.7 ng d/mL). The mean residence time (MRT) in the parasitised group (3.4 +/- 0.3 days) was significantly shorter (P<0.05) than in the healthy group (6.6 +/- 0.6 days). Study results have shown that parasitic disease, through alteration in the body condition, can produce significant changes in the plasma disposition of DRM when administered SC to parasitised lambs.
Pérez
Rubén
R
Laboratorio de Farmacología, Facultad Medicina Veterinaria, Universidad de Concepción, P.O. Box 537 Chillán, Chile. rubperez@udec.cl
Palma
Cristina
C
Araneda
Marcia
M
Cabezas
Ignacio
I
Rubilar
Luis
L
Arboix
Margarita
M
D000818:Animals; D000871:Anthelmintics / Q000493:pharmacokinetics*; D001682:Biological Availability; D005243:Feces / Q000469:parasitology; D005767:Gastrointestinal Diseases / Q000469:parasitology / Q000662:veterinary*; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D010270:Parasite Egg Count; D012756:Sheep; D012757:Sheep Diseases / Q000188:drug therapy / Q000469:parasitology*
D000871:Anthelmintics; D007559:Ivermectin; C084101:doramectin