Tilmicosin enteric granules and premix to pigs: Antimicrobial susceptibility testing and comparative pharmacokinetics

Study on the Metabolic Transformation Rule of Enrofloxacin Combined with Tilmicosin in Laying Hens

There is often abuse of drugs in livestock and poultry production, and the improper use of drugs leads to the existence of a low level of residues in eggs, which is a potential threat to human safety. Enrofloxacin (EF) and tilmicosin (TIM) are regularly combined for the prevention and treatment of poultry diseases. The current studies on EF or TIM mainly focus on a single drug, and the effects of the combined application of these two antibiotics on EF metabolism in laying hens are rarely reported. In this study, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine the residual EF and TIM in laying hens and to investigate the effect of TIM on the EF metabolism in laying hens. In this paper, we first establish a method that can detect EF and TIM simultaneously. Secondly, the results showed that the highest concentration of EF in the egg samples was 974.92 ± 441.71 μg/kg on the 5th day of treatment. The highest concentration of EF in the egg samples of the combined administration group was 1256.41 ± 226.10 μg/kg on the 5th day of administration. The results showed that when EF and TIM were used in combination, the residue of EF in the eggs was increased, the elimination rate of EF was decreased, and the half-life of EF was increased. Therefore, the use of EF and TIM in combination should be treated with greater care and supervision should be strengthened to avoid risks to human health.

Pharmacokinetic and Pharmacodynamic integration of tilmicosin against Mycoplasma gallisepticum in the target infection site in chickens

Mycoplasma gallisepticum (M. gallisepticum) is a primary respiratory pathogen of poultry and causes significant economic losses to the poultry industry. There were no reported articles concerning the Pharmacokinetics/Pharmacodynamics (PK/PD) interactions of tilmicosin against M. gallisepticum in vivo. In the current study, we established an in vivo M. gallisepticum infection model and tilmicosin was administered orally to the M. gallisepticum-infected chickens by different dosage regimens. The concentration of tilmicosin in lung tissue was determined by high-pressure liquid chromatography/tandem mass spectrometry (HPLC–MS/MS), besides the counting of the viable colony of M. gallisepticum in lung tissue was also monitored dynamically to appraise the PK/PD interactions of tilmicosin against M. gallisepticum. We found that anti-mycoplasmal activity was concentration-dependent and mycoplasmacidal activity was observed at tilmicosin dosage >7.5 mg/kg. The PK/PD parameter of AUC/MIC (The area under the concentration–time curve divided by the minimal inhibitory concentration) correlated well with anti-mycoplasmal efficacy (R² = 0.92). The ratios of AUC/MIC for 1 log₁₀ and 3 log₁₀ colony-forming units [CFU]/lung reductions were 300.02 and 6,950.15 h, respectively. These findings indicated that tilmicosin may be therapeutically effective in chickens to treat M. gallisepticum lung infections if administered at a dose of 9.12 mg/kg.

Optimization of Tilmicosin-Loaded Nanostructured Lipid Carriers Using Orthogonal Design for Overcoming Oral Administration Obstacle

Tilmicosin (TMS) is widely used to treat bacterial infections in veterinary medicine, but the clinical effect is limited by its poor solubility, bitterness, gastric instability, and intestinal efflux transport. Nanostructured lipid carriers (NLCs) are nowadays considered to be a promising vector of therapeutic drugs for oral administration. In this study, an orthogonal experimental design was applied for optimizing TMS-loaded NLCs (TMS-NLCs). The ratios of emulsifier to mixed lipids, stearic acid to oleic acid, drugs to mixed lipids, and cold water to hot emulsion were selected as the independent variables, while the hydrodynamic diameter (HD), drug loading (DL), and entrapment efficiency (EE) were the chosen responses. The optimized TMS-NLCs had a small HD, high DL, and EE of 276.85 ± 2.62 nm, 9.14 ± 0.04%, and 92.92 ± 0.42%, respectively. In addition, a low polydispersity index (0.231 ± 0.001) and high negative zeta potential (-31.10 ± 0.00 mV) indicated the excellent stability, which was further demonstrated by uniformly dispersed spherical nanoparticles under transmission electron microscopy. TMS-NLCs exhibited a slow and sustained release behavior in both simulated gastric juice and intestinal fluid. Furthermore, MDCK-chAbcg2/Abcb1 cell monolayers were successfully established to evaluate their absorption efficiency and potential mechanism. The results of biodirectional transport showed that TMS-NLCs could enhance the cellular uptake and inhibit the efflux function of drug transporters against TMS in MDCK-chAbcg2/Abcb1 cells. Moreover, the data revealed that TMS-NLCs could enter the cells mainly via the caveolae/lipid raft-mediated endocytosis and partially via macropinocytosis. Furthermore, TMS-NLCs showed the same antibacterial activity as free TMS. Taken together, the optimized NLCs were the promising oral delivery carrier for overcoming oral administration obstacle of TMS.

Pharmacokinetics and bioavailability of solid dispersion formulation of tilmicosin in pigs

Tilmicosin (TMS) is a semisynthetic macrolide antibiotic restricted to veterinary use but is only partially soluble in aqueous solutions, which limits its administration in treatments. We developed a strategy to enhance the supersaturated solubility of TMS using amorphous solid dispersion (SD). The dissolution profile shown that the dissolution rate of TMS-SD was obviously faster than TMS. The pharmacokinetics of tilmicosin (TMS) and tilmicosin solid dispersion (TMS-SD) in pigs after oral administration at a single dose of 50 mg/kg b.w were investigated. The t_max of TMS-SD (2.50 hr) was 1.80 times faster than TMS (4.50 hr) (p < .05). There were no significant differences in the other PK parameters (C_max , t_1/2β , V/F, CL/F, MRT, and AUC_0-inf ) (p > .05). The mean relative bioavailability of TMS-SD compared with TMS was 140.39%, according to the AUC_0-inf values. These results demonstrated that the solid dispersion technique enhanced the bioavailability of TMS and the new formulation administered to animals via drinking water may be used as a therapeutic alternative for clinical treatments.

Urinary antibiotic exposure across pregnancy from Chinese pregnant women and health risk assessment: Repeated measures analysis

Multiple antibiotics are widely used in clinic practice and livestock husbandry, but exposure data based on repeated measurements are scarce among pregnant women. Here, we biomonitored 41 antibiotics and their two metabolites in urine samples from 3235 pregnant women over three trimesters. Spearman's correlation coefficient, intraclass correlation coefficient (ICC), percentile analysis and linear mixed models were employed to evaluate the correlations, variability, co-exposure patterns and predictors of antibiotics, respectively. Pregnant urinary creatinine-adjusted concentrations of antibiotics were used to estimate daily exposure dose and assessed health risks. The target antibiotics were detected in more than 90% of urine samples, primarily as preferred as veterinary antibiotics (PVAs), and the 95th percentile urinary concentrations of each individual antibiotics were range from below the limits of detection to 5.74 ng/mL. We observed considerable within-subject variation (ICC: 0.05-0.63) of urinary antibiotics concentrations during pregnancy. More than half pregnant women were co-exposed to two or more antibiotics of different usage classes, while both co-exposure to high percentiles of three usage antibiotics at one trimester or exposure to single usage antibiotics at high-dose through three trimesters were infrequent in the study population, and most pregnant women were continuously exposed to low-dose PVAs across pregnancy. A total of 4.5% samples were showed hazard index values exceeding 1 during entire pregnancy. Urinary levels of antibiotics associated with residence, maternal age and education, pre-pregnancy BMI, household income and gestational week, especially vary by sampling seasons. Taken together, most pregnant women were frequently exposure to low-dose PVAs across pregnancy and some were in a health risk associated with the disturbance of gut microbiota. Multiple measurements of urinary antibiotic concentrations are essential to more accurate charactering the exposure levels during pregnancy. Several predictors of urinary antibiotics should be taken into consideration in future researches.

Pharmacokinetics and bioavailability of tildipirosin in rabbits following single-dose intravenous and intramuscular administration

The objective of this study was to determine the pharmacokinetics of tildipirosin in rabbits after a single intravenous (i.v.) and intramuscular (i.m.) injection at a dose of 4 mg/kg. Twelve white New Zealand rabbits were assigned to a randomized, parallel trial design. Blood samples were collected prior to administration and up to 14 days postadministration. Plasma concentrations of tildipirosin were quantified using a validated ultra-high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method. The pharmacokinetic parameters were calculated using a noncompartmental model in WinNonlin 5.2 software. Following i.v. and i.m. administration, the elimination half-life (T_1/2λ ) was 81.17 ± 9.28 and 96.68 ± 15.37 hr, respectively, and the mean residence time (MRT_last ) was 65.44 ± 10.89 and 67.06 ± 10.49 hr, respectively. After i.v. injection, the plasma clearance rate (Cl) and volume of distribution at steady state (V_dss ) were 0.28 ± 0.10 L kg^-1  h^-1 and 17.78 ± 5.15 L/kg, respectively. The maximum plasma concentration (C_max ) and time to reach maximum plasma concentration (T_max ) after i.m. administration were 836.2 ± 117.9 ng/ml and 0.33 ± 0.17 hr, respectively. The absolute bioavailability of i.m. administration was 105.4%. Tildipirosin shows favorable pharmacokinetic characteristics in rabbits, with fast absorption, extensive distribution, and high bioavailability. These findings suggest that tildipirosin might be a potential drug for the prevention and treatment of respiratory diseases in rabbits.

Comparison of the pharmacokinetics of tilmicosin in plasma and lung tissue in healthy chickens and chickens experimentally infected with Mycoplasma gallisepticum

The objectives of this study were to compare the plasma and lung tissue pharmacokinetics of tilmicosin in healthy and Mycoplasma gallisepticum-infected chickens. Tilmicosin was orally administered at 4, 7.5 and 10 mg/kg body weight (b.w) for the infected and 7.5 mg/kg b.w for the uninfected control group. We found no significant differences in plasma tilmicosin pharmacokinetics between diseased and healthy control chickens. In contrast, the lung tissues in M. gallisepticum-infected chickens displayed a t_1/2 (elimination half-life) 1.76 times longer than for healthy chickens. The C_max (the maximum concentration of drug in samples) of tilmicosin in M. gallisepticum-infected chickens was lower than for controls at 7.5 mg/kg b.w (p < .05), and the AUC_inf (the area under the concentration-time curve from time 0 extrapolated to infinity) in infected chickens was higher than for the healthy chickens (p < .05). The mean residence time of tilmicosin in infected chickens was also higher than the healthy chickens. These results indicated that the lungs of healthy chickens had greater absorption of tilmicosin than the infected chickens, and the rate of elimination of tilmicosin from infected lungs was slower.

Efficacy of enteric-coated tilmicosin granules in pigs artificially infected with Actinobacillus pleuropneumoniae serotype 2

BACKGROUND

Porcine infectious pleuropneumonia caused by Actinobacillus pleuropneumoniae (App) is one of the most serious infectious diseases in pigs and has brought huge economic losses to the world pig industry. The aim of this trial was to evaluate the effect of enteric-coated tilmicosin granule in the treatment and control of artificial infection of App.

METHODS

Sixty Duroc and Yorkshire crossbred pigs (50 of which were artificially infected) were divided into six groups: BCG (Blank control group), ICG (Infection-only control group), HDG (High-dose enteric-coated tilmicosin granules), MDG (Medium-dose enteric-coated tilmicosin granules), LDG (Low-dose enteric-coated tilmicosin granules) and TPG (Tilmicosin premix drug control group). The cure rate, mortality, clinical respiratory score, body temperature score, weight gain, lung score and so on were recorded.

RESULTS

The cure rate of HDG and MDG was as high as 90%, the mortality was 10%, and the clinical signs recovered quickly.

CONCLUSION

The results showed that enteric-coated tilmicosin granules had obvious therapeutic effect on artificial infection, which could reduce the damage caused by the disease and reduce the mortality.

Comparison of pharmacokinetics of tilmicosin in healthy pigs and pigs experimentally infected with Actinobacillus pleuropneumoniae

Aim: To compare the pharmacokinetic profiles of tilmicosin, administered orally at a single dose of 20 mg/kg bodyweight, in healthy pigs and in pigs experimentally infected with Actinobacillus pleuropneumoniae. Methods: Twelve healthy crossbred pigs, aged approximately 8 weeks, were randomly assigned to uninfected and infected groups, with six pigs per group. Pigs in the infected group were inoculated intranasally with a bacterial suspension of A. pleuropneumoniae containing approximately 10⁸ cfu. Each pig received a single oral dose of 20 mg/kg bodyweight of tilmicosin, given 3-4 hours after inoculation in infected pigs. Blood samples were collected before drug administration and up to 48 hours after tilmicosin administration. Concentrations of tilmicosin in plasma samples were determined by HPLC. Throughout the experimental period pigs were observed for signs of inappetence and clinical abnormalities. After sampling was complete pigs were subject to euthanasia and samples collected for gross and histopathology as well as microbiology. Results: Infected pigs showed signs of bradykinesia, nasal discharge dyspnoea, and coughing 1 hours after inoculation and A. pleuropneumoniae was cultured from the lungs of all infected pigs postmortem. Comparing pharmacokinetic parameters in uninfected and infected pigs, the maximum plasma concentration of tilmicosin was higher in uninfected pigs (1.17 (SD 0.17) vs. 0.96 (SD 0.17) µg/mL), the time to reach maximum concentration was shorter (1.53 (SD 0.23) vs. 2.40 (SD 0.37) hours), and the half-life of the absorption phase and half-life of the elimination phase were both shorter (0.66 (SD 0.08) vs. 1.00 (SD 0.27) hours) and (12.93 (SD 0.96) vs. 16.53 (SD 0.55) hours), respectively. The apparent volume of distribution was smaller in uninfected than infected pigs (1.91 (SD 0.22) vs. 2.16 (SD 0.21) L/kg). The relative bioavailability of tilmicosin in infected relative to uninfected pigs was 108.6 (SD 9.71)%. Conclusions and clinical relevance: The results of this study indicate that A. pleuropneumoniae infection significantly changed certain pharmacokinetic parameters of tilmicosin in pigs. In infected pigs tilmicosin exhibited a longer drug persistence and a better extent of absorption. These results indicate that it is necessary to monitor and adjust the dose of tilmicosin administration during the presence of pleuropneumonia. It is expected that this can optimise clinical efficacy and help avoid the development of resistance.