Pharmacokinetics and bioavailability of tulathromycin following intravenous, intramuscular and subcutaneous administrations in healthy rabbits

Aim: This work was performed to investigate the pharmacokinetics of the triamilide antibiotic, tulathromycin in healthy rabbits. Materials and Methods: Ten rabbits in each group were given a single dose of 2.5 mg/kg body weight (bw) of tulathromycin via intravenous (IV), intramuscular (IM) and subcutaneous (SC) administrations. The concentration of tulathromycin in plasma was determined by microbiological assay Bacillus subtilis ATCC 6633 as the test organism. Results: Following IV administration, the total body clearance (Cl) was 321.70 ml/kgh, the volume of distribution at tot steady-state (V-dss) was 13.26 L/kg and the value of the elimination half-life (t(1/2 beta)) was 29.29 h. After SC administration, the elimination half-life (t(1/2el)), mean residence time (MRT) and maximum plasma concentration (C-max) were significantly higher (36.22 h, 52.54 h and 882.19 ng/ml) than after IM route (31.69 h, 45.89 h and 714.72 ng/ml), respectively. Tulathromycin was bound to the extent of 36% to plasma protein of healthy rabbits. The absolute bioavailabilities were 88.07 and 94.25% after IM and SC injections. Conclusion: Thus a single dose of tulathromycin is promising treatment for most respiratory disease in rabbits.