Pharmacokinetics of tilmicosin in chicken joints based on a novel microdialysis sampling method

Residue depletion and withdrawal time estimation of tilmicosin in black-bone silky fowls after administration via drinking water

In this study, residue depletion and withdrawal time estimation of tilmicosin were examined in Taihe black-bone silky fowls (TBSFs) after oral administration for three consecutive days at a dose of 75 mg/L in water. The tilmicosin concentrations in liver, kidney, muscle, and skin/fat of TBSFs collected from different time points (0.16, 1, 3, 5, 7, 9, 12, 20, 30, 40 days after last administration) were determined by UPLC-MS/MS. The results indicated that the tilmicosin concentrations in TBSFs tissues varied significantly, and kidney had the highest average concentrations (2604.65 ± 4625.20 μg/kg), followed by liver (1125.54 ± 1479.24 μg/kg), skin/fat (372.81 ± 428.33 μg/kg), and muscle (104.52 ± 143.95 μg/kg). Meanwhile, tilmicosin was still detected in all the four studied tissues (liver, kidney, skin/fat, and muscle) of TBSFs at the last time point (40th day after administration), suggesting that tilmicosin in TBSFs depleted slowly. Based on our experiments, the recommended withdrawal time of tilmicosin for TBSFs after oral administration for three consecutive days at a dose of 75 mg/L in water should be 32 days, which is much longer than the duration specified by Chinese regulatory authorities (10 days), and the abundance of melanin in TBSFs might be responsible for this phenomenon. Hence, a special use and withdrawal procedure of veterinary drugs in TBSFs is needed, and it is essential to focus on potential involvement of melanin in tilmicosin accumulation.

Application of microdialysis combined with lipidomics to analyze fatty acid metabolic changes in the disease process of rheumatoid arthritis

Rheumatoid arthritis (RA) is a metabolically active disease, with shifts in fatty acid metabolism during disease progression profoundly affecting the systemic inflammatory response. Altered fatty acid biomarker metabolism may be a key target for the treatment of RA. To investigate the changes of fatty acid metabolism in RA, collagen-induced arthritis (CIA) model was established. Microdialysis sampling was utilized to overcome the characteristic of occlusive joint cavity in vivo synovial fluid (SF) sampling. Lipidomic methods were established with the UHPLC-Orbitrap Exploris120 platform, and lipid measurements were performed on serum and SF samples. Then, multivariate statistical analyses were performed to detect changes in lipid metabolites induced by CIA. Consequently, a total of 22 potential biomarkers associated with differential fatty acids were screened and identified in serum, and 13 were identified in SF. Notably, alterations were observed in metabolites such as Hexadecanoic acid, Octadecanoic acid, Arachidonic acid, (+/-)11,12-EpETrE, DHA, DPA, Myristic acid, Suberic acid, and others. This study explored a new mechanism of the RA disease process from the perspective of fatty acid metabolism. It provided a new strategy for experimental research on determining the optimal time for establishing CIA model and screening clinical diagnostic biomarkers.

The pharmacokinetics/pharmacodynamics integration of tilmicosin against Mycoplasma synoviae in vitro and in vivo

Mycoplasma synoviae (MS) infection is a serious threat to poultry industry in China. Tilmicosin is a semisynthetic macrolide antibiotic used only in animals and has shown potential efficacy against MS, but there were no reported articles concerning the pharmacokinetics/pharmacodynamics (PK/PD) interactions of tilmicosin against MS in vitro and vivo. This study aimed to assess the antibacterial activity of tilmicosin against MS in vitro and in vivo using PK/PD model to provide maximal efficacy. The minimum inhibitory concentration (MIC) and killing rates of different drug concentrations were measured using the microdilution method in vitro. Then, tilmicosin was administered orally to the MS-infected chickens at doses of 7.5 and 60 mg/kg, and the PK parameters of tilmicosin in joint dialysates were determined using high-pressure liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) combined with the microdialysis technique. The antibacterial effect (△E) was calculated when the infected chickens were administered a single oral dose of tilmicosin at 4, 7.5, 15, 30, and 60 mg/kg b.w. The PK and PD data were fitted using the Sigmoid Emax model to evaluate the PK/PD interactions of tilmicosin against MS. The bactericidal activity of tilmicosin against MS was concentration dependent. Furthermore, the PK/PD index of AUC0-72h/MIC exhibited the most optimal fitting results (R2 = .98). The MS load decreased by 1, 2, and 3 Log10 CFU/mL, then AUC/MIC was determined as 13.99, 20.53, and 28.23 h, respectively, and the bactericidal effect can be achieved when the dose of MS-infected chickens is at 31.64 mg/kg b.w. The findings of this study hold significant implications for optimizing the treatment regimen for MS infection.

Pharmacokinetics of tilmicosin in plasma, urine and feces after a single intragastric administration in donkey (Equus asinus)

Tilmicosin, a macrolide antibiotic, has the potential to treat bacterial infections in donkeys. However, the pharmacokinetics of tilmicosin in donkeys have not been reported. The aim of this study was to investigate the pharmacokinetics of tilmicosin in donkey plasma, urine, and feces after a single intragastric administration to determine the suitability of tilmicosin for donkeys. A total of 5 healthy male donkeys with similar body weights were selected. The donkeys were administered a single dose of 10 mg · kg-1 body weight (BW) tilmicosin by gavage. The concentrations of tilmicosin in plasma, urine, and feces were determined. The results showed that after a single intragastric administration of 10 mg · kg-1 body weight, tilmicosin in donkey plasma reached a maximum concentration of 11.23 ± 5.37 mg · L-1 at 0.80 ± 0.10 h, with a half-life of 14.49 ± 7.13 h, a mean residence time of 28.05 ± 3.05 h, a Cl/F of 0.48 ± 0.18 L · kg-1 · h-1, and a Vd/F of 9.28 ± 2.63 Lkg-1. The percentage of tilmicosin excreted through the urine of donkeys is 2.47%, and the percentage excreted through the feces is 66.43%. Our study provides data to inform the use of tilmicosin in donkeys.