DISPOSITION KINETICS AND CLINICAL RESPONSE OF LONG ACTING OXYTETRACYCLINE IN BUFFALOES SUFFERING FROM SUBCLINICAL MASTITIS

Abstract

Disposition kinetics and clinical response of long acting oxytetracycline (Terramycin/La) 20mg/kg body weight intramuscular dose was investigated in buffaloes suffering from sub-clinical mastitis. The blood and milk samples were collected at different time intervals and the kinetic parameters were calculated with a computer program. Absorption half-life for plasma was 1.92 ± 0. 78 hours (mean ± SD) and milk 7.17 ± 3.46 hours. Cmax in plasma was 7.36 ± 1.40 and in milk was 4.86 ± 1.90 1-'g/ml. After distribution equilibrium phase I half-life value was 3.92 ± 3.06 hours for plasma and 7.57 ± 3.23 hours for milk. The elimination half-life (Phase II) was 38.25 ± 18.85 for plasma and 63.34 ± 64.13 for milk. Total body clearance was 100 ± 20 ml. h- 1 • kg- 1 for milk. Somatic cells count in the mastitic buffaloes at the start of experiment was 4.46 ± 0. 73 millions/ml milk. Following intramuscular injection ofTerramycin/La, the cells counts on day 1, 2, 3, 4, 5, 12 and 19 were 4.25 ± 0.14, 3.21 ± 0.17, 2.27 ±0.41, 2.23 ± 0.26, 1.95 ± 0.18, 1.70 ± 0.23 and 1.33 ± 0.36 millions/ml milk. The cells count declined rapidly until day 3 after injection and was related to the plasma and milk levels of the drug, which persisted above MIC level during the 7-8 days observation period. The therapeutic level or minimum inhibitory concentration of the drug in milk and plasma was maintained until 84 hours.