Pharmacokinetics of oxytetracycline long-acting on plasma and semen of beef bulls

The objectives of this investigation were to evaluate the pharmacokinetic parameters of oxytetracycline long-acting in plasma and seminal plasma after a single administration through either subcutaneous or intramuscular route at 10 mg/kg or 20 mg/kg dose. Four Simmental bulls, healthy and satisfactory potential breeders, were used. The route of administration either subcutaneous or intramuscular did not affect the mean values for 10 mg/kg dose in plasma (1,470 ng/mL vs. 1,330 ng/mL; P = 0.82) or seminal plasma (5,710 ng/mL vs. 5,390 ng/mL; P = 0.88), or for 20 mg/kg dose in plasma (2,540 ng/mL vs. 2,590 ng/mL; P = 0.96) or seminal plasma (25,600 ng/mL vs. 19,400 ng/mL; P = 0.58), respectively. Comparison between the 10 mg/kg and 20 mg/kg doses showed a difference in terms of mean plasma levels (1400 ng/mL vs. 2570 ng/mL; P = 0.07) and mean seminal plasma levels (6,480 ng/mL vs. 26,200 ng/mL; P = 0.004), respectively. After the dose of 10 mg/kg, plasma C-max was 2,841 ng/mL at 12 h (T-max) with a half-life of 20.1 h; seminal plasma C-max was 11,515 ng/mL at 24 h (T-max) with a half-life of 23.7 h. After the dose of 20 mg/kg, plasma C-max was 5,269 ng/mL at 12 h (T-max) with a half-life of 18.1 h; seminal plasma C-max was 55,040 ng/mL at 24 h (T-max) with a half-life of 15.7 h. Oxytetracycline long-acting may be an appropriate antibiotic, owing to its pharmacokinetic properties, that could be used for treating bulls' genital infections when its usage is indicated. (C) 2022 Published by Elsevier Inc.