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A plasma and tissue kinetic study of sulfadiazine (SDZ) and its metabolite, N4‐acetyl sulfadiazine (ACT‐SDZ), was characterized in channel catfish (Ictalurus punctatus) following a single oral dose of 50 mg/kg at 18 and 24°C. Samples were collected at predetermined time points and determined by ultra‐performance liquid chromatography. The classical one‐compartmental method was used to estimate the pharmacokinetic parameters. Results showed that the changing of temperature was markedly influential on the kinetics of SDZ and ACT‐SDZ in plasma and tissues. When the temperature was increased from 18 to 24°C, the elimination half‐life (K10_HF) of SDZ was decreased in gill, kidney, and muscle + skin, but increased in liver and plasma. The K10_HF of ACT‐SDZ also had a decreased trend in gill, liver, and plasma but had comparable values in kidney and muscle + skin. The absorption half‐life (K01_HF), time to peak concentration (Tmax), and area under concentration–time curve (AUC0‐∞) of SDZ and ACT‐SDZ all exhibited declined tendencies in plasma and tissues. The apparent volume of distribution (V_F) of SDZ in plasma was increased from 0.53 to 1.48 L/kg, and the apparent systemic total body clearance (Cl_F) was increased from 0.028 to 0.060 L/h/kg. In a word, K01_HF, Tmax, and AUC0‐∞ of SDZ and ACT‐SDZ were decreased in plasma and tissues with the increase of temperature, whereas the V_F and Cl_F of SDZ were increased. Meanwhile, we calculated the percentage of time profile of SDZ concentration more than minimum inhibitory concentration to total time (%T > MIC) to guide clinical usage of SDZ. When the dosage interval was 24 h, the values of %T > MIC were all >90% in plasma and most tissues. Therefore, we recommend an oral dose of SDZ at 50 mg/kg once per 24 h at 18–24°C against the fish pathogens with an MIC value of ≤6.4 μg/mL. [ABSTRACT FROM AUTHOR]

This study aimed to determine the bioavailability and pharmacokinetic parameters of sulfadiazine (SDZ) in channel catfish (Ictalurus punctatus) following oral gavage and intravenous injection. The healthy channel catfish were orally and intravenously administrated with SDZ solution at doses of 50 and 5 mg/kg, respectively. Plasma samples were determined by ultra‐performance liquid chromatography with an ultraviolet detector. The results demonstrated that the concentration‐time profile of SDZ after oral dosing was best described by a one‐compartmental open model with first‐order absorption. The absorption half‐life (t1/2Kα), the elimination half‐life (t1/2Ke), and the area under concentration‐time profile (AUC0‐∞) were estimated to be 0.87 h, 29.04 h, and 1311.72 mg.h/L, respectively. After intravenous administration, the concentration‐time curve of SDZ conformed to a two‐compartmental open model without absorption. The distribution half‐life (t1/2α), the elimination half‐life (t1/2β), the apparent distribution volume (Vss), the total clearance (CL), and AUC0‐∞ were calculated to be 0.19 h, 14.24 h, 0.36 L/kg, 0.018 L/h/kg, and 277.12 mg.h/L, respectively. Finally, the bioavailability was estimated to be 47.33%. This study will provide some useful information for the modification of the dosage form of SDZ in aquaculture, and is partly beneficial for appropriate use of SDZ in the future. [ABSTRACT FROM AUTHOR]

Tiamulin fumarate (TIF) is a pleuromutilin antibiotic and has high activity against animal bacterial pathogens including aquatic bacterial pathogens. However, its pharmacokinetic profiles, tissue distribution characteristics and bioavailability in aquatic animals remain unknown. The objective of this study was to investigate the pharmacokinetics and tissue distribution regularities of TIF in tilapia (Oreochromis niloticus) following a single oral (PO) dose of 20 mg/kg body weight (bw) and a single intravenous (IV) dose of 5 mg/kg bw at 22 ± 1°C, respectively. TIF concentrations in tilapia plasma and tissues were determined using the isotope dilution HPLC‐HESI‐MS/MS procedure, which was validated according to the guidelines defined by US Food and Drug Administration. TIF was well distributed throughout the body compartments of tilapia judged by the apparent volume of distribution (Vd) >1 L/kg (6.69 L/kg PO and 1.78 L/kg IV). TIF had a short mean residence time (MRT; 22.82 h PO and 14.61 h IV) and quick total body clearance (CLb) (0.62 L kg−1 h−1 PO and 0.60 L kg−1 h−1 IV). The total area under the curve (AUCtot) of plasma were 32.25 μg h−1 ml−1 (PO) and 8.30 μg h−1 ml (IV), respectively, and the oral absolute bioavailability (F%) of TIF was calculated to be approximately 97.1%. For tissue distribution, high concentrations of TIF were found in kidney, and the longest MRT was recorded in bile. The withdrawal time (WT) of TIF in muscle, skin, liver, kidney, gill, and bile was 3.75 (4) and 1.79 (2), 1.77 (2) and 2.06 (3), 6.41 (7) and 1.97 (2), 6.95 (7) and 3.98 (4), 4.92 (5) and 2.36 (3), and 7.06 (8) and 6.16 (7) days after PO and IV administration, respectively. The present investigations indicated that TIF was quickly absorbed, well distributed, rapidly eliminated in tilapia, and it could serve as reference data for establishing use regimen and provide useful information for the further development of TIF in aquaculture. [ABSTRACT FROM AUTHOR]

This study aimed to examine the bioavailability (BA) and pharmacokinetic (PK) characteristics of sulfadiazine (SDZ) in grass carp (Ctenopharyngodon idellus) after oral and intravenous administrations. Blood samples were collected at predetermined time points of 0.083, 0.17, 0.5, 1, 2, 4, 8, 16, 24, 48, 72, and 96 hr (n = 6). The samples were extracted and purified by organic reagents and determined by the ultra‐performance liquid chromatography. The software named 3P97 was used to calculate relevant PK parameters. The results demonstrated that the concentration–time profile of SDZ was best described by a one‐compartmental open model with first‐order absorption after a single oral dose. The main PK parameters of the absorption rate constant (Kα), the absorption half‐life (t1/2 Kα), the elimination rate constant (Ke), the elimination half‐life (t1/2Ke), and the area under concentration–time profile (AUC0‐∞) were 0.3 1/h, 2.29 hr, 0.039 1/h, 17.64 hr, and 855.78 mg.h/L, respectively. Following intravenous administration, the concentration–time curve fitted to a two‐compartmental open model without absorption. The primary PK parameters of the distribution rate constant (α), the elimination rate constant (β), the distribution half‐life (t1/2α), the elimination half‐life (t1/2β), the apparent distribution volume (VSS), the total clearance (CL), and AUC0‐∞ were 9.62 1/hr, 0.039 1/hr, 0.072 hr, 17.71 hr, 0.33 L/kg, 0.013 L h−1 kg−1, and 386.23 mg.h/L, respectively. Finally, the BA was calculated to be 22.16%. Overall, this study will provide some fundamental information on PK properties in the development of a new formulation SDZ in the future and is partially beneficial for the appropriate usage of SDZ in aquaculture. [ABSTRACT FROM AUTHOR]