Amoxycillin, a penicillinase-susceptible semisynthetic penicillin, is bactericidal for both gram-positive and gram-negative bacteria. This antibiotic has also found use in veterinary medicine (BYWATER, 1982; HUBER, 1982). The pharmacokinetics and dosage of amoxycillin have been investigated in different species of domestic animals other than buffaloes (PALMER PUGH, 1977; YEOMAN, 1977;RUTGERS et al., 1980;CARLI et aL, 1981;STANTON et al., 1982). Earlier studies have demonstrated that the dosage regimen of broad spectrum antibiotics recommended for cattle may not be effectively employed in buffalo species (VARMA et al., 1980; VARMA and PAUL, 1983). It was, therefore, considered expedient to investigate the pharmacokinetics and distribution of amoxycillin in buffalo calves. Based on the kinetic data, a dosage regimen of amoxycillin was determined for its rational use in buffalo species.
Material and Methods
Animals and treatmentEighteen healthy male buffalo calves weighing 76-99 kg were acclimatized for 2 weeks in the departmental animal shed and were subjected to regular clinical examination. The animals were maintained on green fodder and wheat straw. Water was available ad libitum.Amoxycillin was injected as sodium amoxycillin (Beecham Labs., Bristol, Tenn) into the jugular vein in a single dose of 10 mg/kg body weight.
Collection of samples and amoxycillin assayBlood samples from each of 8 calves were collected by jugular venipuncture prior to and at 2. 5, 5, 10, 15, 30, 45, 60, 90, 120, 180, 240, 360 and 480 min after injection of the antibiotic. Blood was allowed to clot at room temperature and serum was obtained after centrifugation.In distribution studies, six animals divided into 3 groups were sacrificed at 15, 180 and 360 min after medication and their different body tissues and fluids were collected for amoxycillin assay. For the collection of interstitial fluid, tissue cages were implanted subcutaneously in a group of 4 animals in the region of neck and right flank. One month later, animals were given the antibiotic and samples of interstitial fluid were withdrawn at 0, 1, 2, 4, 6 and 8 h after dosing.The levels of amoxycillin in serum, body tissues and fluids were determined by the standard cylinder cup plate bioassay method using Sarcina lutea (ATCC 9341) as the test organism ( ARRET et al., 1971). The activity was expressed as pg amoxycillin/ml of fluid or g of tissue.U.S.