Pharmacokinetics of tetracycline hydrochloride in fat-tailed sheep

Tetracycline may be used to treat several types of bacterial diseases in ruminants. In addition, tetracycline is added to food to promote the growth. There are few reports on the pharmacokinetics of tetracycline in sheep. Therefore, the objective of this study was to examine the pharmacokinetic characteristics of the drug in sheep. Ten apparently healthy mixed-breed sheep were administered 20 mg/kg tetracycline orally and intravenously with a time interval of two weeks. Blood samples were collected before and at various time intervals after the administration of the drug. Sera were separated, kept at -20°C, and analysed using fluorescence spectrophotometry. The volume of distribution (Vd), elimination rate constant (Kel), half-life (t1/2), and clearance (ClB) of tetracycline after intravenous injection were determined to be 0.21 L/kg, 0.21/hr, 3.3 hr, and 0.73 ml/kg/min, respectively. When the drug was given orally, these parameters were found to be 0.37 L/kg, 0.12/hr, 5.8 hr, and 0.73 ml/kg/min, respectively. Moreover, the bioavailability of tetracycline after oral administration was around 55%.