Pharmacokinetics of tulathromycin after subcutaneous injection in North American bison (Bison bison)

Pharmacokinetics of tulathromycin on plasma and semen of beef bulls

The objective of this investigation was to evaluate the pharmacokinetic parameters of tulathromycin in plasma and semen of beef bulls after administering a single sc dose at two different sites in the neck. Four Simmental bulls with excellent temperament received a comprehensive physical exam that included breeding soundness examination. In addition, blood was collected and analyzed for CBC and chemical panel in order to rule out any subclinical liver or kidney disease. All bulls were diagnosed as healthy and satisfactory potential breeders. The mean plasma levels of tulathromycin for the two neck sites of sc administration were not different between posterior aspect of the ear where it attaches to the head (RP; regio parotidea; 77.9 ± 43.3 ng/mL; X ± SD) and to the middle of the neck (RC; regio collis lateralis; 73.7 ± 39.7 ng/mL; P = 0.84). The mean seminal plasma levels of tulathromycin after administration in the RP was 608 ± 374 ng/mL and for RC was 867 ± 599 ng/mL without differences between both sites (P = 0.29). The mean level of tulathromycin in plasma was 75.8 ± 40.2 ng/mL, which was lower than mean seminal plasma levels of 781 ± 482 ng/mL (P = 0.001). The plasma peak tulathromycin concentration (C_max) was 160 ± 27 ng/mL at 21 ± 6 h (T_max) post-administration. The seminal plasma C_max was 1539 ± 44.4 ng/mL at 33.00 ± 18.00 h (T_max) post-administration. The C_max between plasma and seminal plasma were different (P = 0.008) without any differences in T_max between plasma and seminal plasma (P = 0.35). The terminal half-life for plasma tulathromycin (81.4 ± 27.6 h) showed a tendency to be shorter than in seminal plasma (114.7 ± 21.7; P = 0.10). The plasma area under the curve concentration time from the first to the last sample (AUC_0-last) was 15,440 ± 1717 ng/mL/h, which was significatively smaller compared with 171,071 ± 58,556 ng/mL/h for seminal plasma AUC_0-last (P = 0.01). The plasma means residence time from the first to the last sample (MRT_0-last) was 89.3 ± 5.1 h and it was shorter than for seminal plasma of 96.6 ± 5.0 h (P = 0.05). From the present investigation, it was concluded that tulathromycin is a suitable antibiotic based in its pharmacokinetic properties that could be used for treatment of bull genital infections when its application is indicated.

Effect of age on the pharmacokinetics and distribution of tulathromycin in interstitial and pulmonary epithelial lining fluid in healthy calves

OBJECTIVE To compare the plasma pharmacokinetics of tulathromycin between 3-week-old (preweaned) and 6-month-old (weaned) calves and to characterize the distribution of tulathromcyin into pulmonary epithelial lining fluid (PELF) and interstitial fluid (ISF) of preweaned and weaned calves following SC administration of a single dose (2.5 mg/kg). ANIMALS 8 healthy 3-week-old and 8 healthy 6-month-old Holstein steers. PROCEDURES A jugular catheter and SC ultrafiltration probe were aseptically placed in the neck of each calf before tulathromycin administration. Blood, ISF, and bronchoalveolar lavage fluid samples were collected at predetermined times before and after tulathromycin administration for quantification of drug concentration. A urea dilution method was used to estimate tulathromycin concentration in PELF from that in bronchoalveolar lavage fluid. Tulathromycin-plasma protein binding was determined by in vitro methods. Plasma pharmacokinetics were determined by a 2-compartment model. Pharmacokinetic parameters and drug concentrations were compared between preweaned and weaned calves. RESULTS Clearance and volume of distribution per fraction of tulathromycin absorbed were significantly greater for weaned calves than preweaned calves. Tulathromycin-plasma protein binding was significantly greater for weaned calves than preweaned calves. Maximum PELF tulathromycin concentration was significantly greater than the maximum plasma and maximum ISF tulathromycin concentrations in both groups. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that age affected multiple pharmacokinetic parameters of tulathromycin, likely owing to physiologic changes as calves mature from preruminants to ruminants. Knowledge of those changes may be useful in the development of studies to evaluate potential dose adjustments during treatment of calves with respiratory tract disease.