D. Dimitrova V. Кatsarov, D. Dimitrov, D. Tsoneva

Abstract. Investigation of the pharmacokinetics of tiamulin hydrogen fumarate and chlortetracycline hydrochloride after single oral application of the preparation Tetramutin-premix in pigs. 8 clinically healthy pigs at the age of 10 weeks, from both genders, weighing 20.3 kg on average (15 tо 24.5 kg). Pigs were treated once orally with Tetramutin-premix, at a dose of 25 mg/kg tiamulin hydrogen fumarate and 75 mg/kg chlortetracycline hydrochloride. Serum concentrations of tiamulin and chlortetracycline were assayed by validated microbiological and HPLC methods, respectively. The main pharmacokinetic parameters of both antibiotics were calculated. The pharmacokinetic parameters of tiamulin (mean±SEM) determined by both compartmental and noncompartmental methods, were as followed: elimination half-life (t )–4.68 0.62 and 5.05 0.31 h; mean residence time (MRT)8.20 0.72 h and 8.20 0.40 h; 1/2´ maximum serum concentrations (C )–1.880.11 and 1.90±0.14 μg.h/ml; time to reach maximum serum concentrations (T ) – 2.46±0.20 h and 2.11±0.01 h; max max area under the concentration-time curve (AUC )–17.23±0.72 and 17.65±1.74 μg.h/ml. Serum tiamulin concentrations higher than 0.10 g/ml were detected 0→∞ in all treated pigs up to the 12th hour, and in some animals–by the 24th h. The respective Mean + SEM pharmacokinetic parameters of chlortetracycline after administration of Tetramutin-premix, determined by both compartmental and non-compartmental methods were: t – 3.92±0.24 h and 4.35±0.10 h; 1/2´ C –4.65±0.14 g/ml and 5.12±0.20 μg.h/ml.; T –2.99±0.09 h and 3.00±0.11 h; area under the time-concentration curve – 43.97±0.18 g.h/ml and max max 44.06±0.12 μg.h/ml. Serum tetracycline levels higher than the minimum detectable ones (10 ng/ml) were detected in all treated animals until the 24th hour.