Comparative pharmacokinetics of florfenicol in the chicken, pigeon and quail

A review on the antibiotic florfenicol: Occurrence, environmental fate, effects, and health risks

Florfenicol, as a replacement for chloramphenicol, can tightly bind to the A site of the 23S rRNA in the 50S subunit of the 70S ribosome, thereby inhibiting protein synthesis and bacterial proliferation. Due to the widespread use in aquaculture and veterinary medicine, florfenicol has been detected in the aquatic environment worldwide. Concerns over the effects and health risks of florfenicol on target and non-target organisms have been raised in recent years. Although the ecotoxicity of florfenicol has been widely reported in different species, no attempt has been made to review the current research progress of florfenicol toxicity, hormesis, and its health risks posed to biota. In this study, a comprehensive literature review was conducted to summarize the effects of florfenicol on various organisms including bacteria, algae, invertebrates, fishes, birds, and mammals. The generation of antibiotic resistant bacteria and spread antibiotic resistant genes, closely associated with hormesis, are pressing environmental health issues stemming from overuse or misuse of antibiotics including florfenicol. Exposure to florfenicol at μg/L-mg/L induced hormetic effects in several algal species, and chromoplasts might serve as a target for florfenicol-induced effects; however, the underlying molecular mechanisms are completely lacking. Exposure to high levels (mg/L) of florfenicol modified the xenobiotic metabolism, antioxidant systems, and energy metabolism, resulting in hepatotoxicity, renal toxicity, immunotoxicity, developmental toxicity, reproductive toxicity, obesogenic effects, and hormesis in different animal species. Mitochondria and the associated energy metabolism are suggested to be the primary targets for florfenicol toxicity in animals, albeit further in-depth investigations are warranted for revealing the long-term effects (e.g., whole-life-cycle impacts, multigenerational effects) of florfenicol, especially at environmental levels, and the underlying mechanisms. This will facilitate the evaluation of potential hormetic effects and construction of adverse outcome pathways for environmental risk assessment and regulation of florfenicol.

Oral pharmacokinetics of a pharmaceutical preparation of florfenicol in broiler chickens

Introduction

The use of florfenicol must follow particular pharmacokinetic/pharmacodynamic (PK/PD) ratios, i.e., it requires achieving serum concentrations at or slightly above the pathogen's minimum inhibitory concentration (MIC) during the dosing interval and that the ratio of area under the concentration vs. time curve (AUC)/MIC should be as high as possible (still undetermined for poultry). As an alternative to the standard soluble florfenicol that is administered to the flock through drinking water, florfenicol premix is often recommended as feed medication in Latin America. However, no particular pharmaceutical design has been proposed.

Methods

This study compared the PK of two preparations of florfenicol in broiler chickens and pondered the possibility of each covering the referred PK-PD ratios as predictors of clinical efficacy. The preparations comprise a pharmaceutical form as FOLA pellets (F = bioavailability; O = optimum; and LA = long-acting) and the premix formulation. The former are small colored pellets with vehicles and absorption enhancers of florfenicol designed for long action, and the latter is the reference premix of the antibiotic. First, these two pharmaceutical forms of florfenicol were administered as oral boluses (30 mg/kg), aided by a probe. In a second trial of the dosing form, both pharmaceutical preparations of florfenicol were administered in feed and ad libitum (110 ppm; ~30 mg/kg).

Results

In both cases, FOLA-florfenicol presented much higher relative bioavailability (3.27 times higher) and mean better residence time than florfenicol premix (two times high when forced as bolus dose). Consequently, FOLA-florfenicol possesses better PK/PD ratios than less sensitive pathogens, i.e., E. coli. It is proposed that if a metaphylactic treatment of a bacterial outbreak in poultry is implemented with florfenicol prepared as FOLA, better PK/PD ratios will be obtained than those of standard florfenicol premix.

Discussion

Clinicians must confirm that feed consumption in the flock has not been affected by the particular disease if FOLA pellets of florfenicol are used.

Old Antibiotics Can Learn New Ways: A Systematic Review of Florfenicol Use in Veterinary Medicine and Future Perspectives Using Nanotechnology

Florfenicol is a broad-spectrum bacteriostatic antibiotic used exclusively in veterinary medicine in order to treat the pathology of farm and aquatic animals. It is a synthetic fluorinated analog of thiamphenicol and chloramphenicol that functions by inhibiting ribosomal activity, which disrupts bacterial protein synthesis and has shown over time a strong activity against Gram-positive and negative bacterial groups. Florfenicol was also reported to have anti-inflammatory activity through a marked reduction in immune cell proliferation and cytokine production. The need for improvement came from (1) the inappropriate use (to an important extent) of this antimicrobial, which led to serious concerns about florfenicol-related resistance genes, and (2) the fact that this antibiotic has a low water solubility making it difficult to formulate an aqueous solution in organic solvents, and applicable for different routes of administration. This review aims to synthesize the various applications of florfenicol in veterinary medicine, explore the potential use of nanotechnology to improve its effectiveness and analyze the advantages and limitations of such approaches. The review is based on data from scientific articles and systematic reviews identified in several databases.

A generic avian physiologically-based kinetic (PBK) model and its application in three bird species

Physiologically-based kinetic (PBK) models are effective tools for designing toxicological studies and conducting extrapolations to inform hazard characterization in risk assessment by filling data gaps and defining safe levels of chemicals. In the present work, a generic avian PBK model for male and female birds was developed using PK-Sim and MoBi from the Open Systems Pharmacology Suite (OSPS). The PBK model includes an ovulation model (egg development) to predict concentrations of chemicals in eggs from dietary exposure. The model was parametrized for chicken (Gallus gallus), bobwhite quail (Colinus virginianus) and mallard duck (Anas platyrhynchos) and was tested with nine chemicals for which in vivo studies were available. Time-concentration profiles of chemicals reaching tissues and egg compartment were simulated and compared to in vivo data. The overall accuracy of the PBK model predictions across the analyzed chemicals was good. Model simulations were found to be in the range of 22-79% within a 3-fold and 41-89% were within 10- fold deviation of the in vivo observed data. However, for some compounds scarcity of in-vivo data and inconsistencies between published studies allowed only a limited goodness of fit evaluation. The generic avian PBK model was developed following a "best practice" workflow describing how to build a PBK model for novel species. The credibility and reproducibility of the avian PBK models were scored by evaluation according to the available guidance documents from WHO (2010), and OECD (2021), to increase applicability, confidence and acceptance of these in silico models in chemical risk assessment.

The influence of the site of drug administration on florfenicol pharmacokinetics in turkeys

Florfenicol is a broad-spectrum antibacterial drug used in the treatment of farm animals, including poultry. This drug is poorly soluble in water, therefore, administration in drinking water may lead to high variability of concentrations in treated individuals. The use of injection preparations, however, requires individual administration and may have a negative effect on the quality of the carcass. In addition, the renal portal system in birds may reduce the bioavailability of the drug administered in the caudofemoral region of the body. The aim of this study was to compare the pharmacokinetics of florfenicol in turkeys after a single intravenous, intramuscular, and subcutaneous administration at a dose of 15 mg/kg body weight. Additionally, to evaluate the effect of renal portal system on drug kinetics, the intramuscular administration was divided into pectoral and caudofemoral administration. The study showed that the area under the concentration-time curve (AUC) was similar regardless of the route of administration. The mean values for clearance and volume of distribution were 0.33 L/kg/h and 0.92 L/kg, respectively. The mean residence time (MRT) was 2.87 h for an intravenous bolus, while for the extravascular administrations it was approx. 5.5 h. The elimination half-life was approx. 4 h regardless of the route of administration. The maximum plasma concentration did not differ statistically between intramuscular (approx. 6.8 mg/L) and subcutaneous (8.2 mg/L) administrations, while the time to appear for this concentration was the longest for caudofemoral administration (1.5 h). The bioavailability was 88.64% for subcutaneous administration, 77.95% for pectoral administration and 85.30% for caudofemoral administration. Overall, all 3 routes of extravascular administration allowed for efficient drug absorption. There was no evidence of an influence of the renal portal system on the kinetic parameters of the drug administered to the lower extremities of the body.

The co-administration effects of florfenicol and lasalocid on performance, biochemical and pathological parameters of muscle, heart, liver, kidney and sciatic nerve in broiler chickens

The study aimed to examine the effect of simultaneous application of florfenicol and lasalocid on the performance and vital organ function of chickens. For this, 300 chicks were divided into four groups. Group one to three received florfenicol, lasalocid and lasalocid plus florfenicol, respectively. Group four as the control group received a basic diet without lasalocid or florfenicol. Lasalocid was used from 7 to 35 days old, continuously. Florfenicol was used at 21 days old for 5 days. The growth indices were measured at the end of each week. The chickens were euthanized at the ages of 28 and 35 days old after collecting blood samples with and without anticoagulants. The liver, heart, muscle, kidney and sciatic nerve were collected in formalin 10% for histopathological examination. The blood and serum samples were used to determine clinical pathologic and hematologic indices. The ratio of internal organs to body weight and ratio of the right ventricle to the total ventricles (RV/TV) of the heart was measured. Results showed, the use of lasalocid decreased feed conversion rate and triglyceride, and increased total protein. Simultaneous administration of lasalocid and florfenicol affected histopathology of the liver and heart and significantly increased creatine phosphokinase, uric acid and the ratio of RV/TV of heart. The eosinophil percentage in the chickens who received florfenicol plus lasalocid was significantly higher than chickens who received florfenicol alone (p < 0.05). In conclusion, it seems that simultaneous administration of the florfenicol and lasalocid induces side‐effects especially on cardiac function and it is not recommended.

Assigning Defined Daily/Course Doses for Antimicrobials in Turkeys to Enable a Cross-Country Quantification and Comparison of Antimicrobial Use

Antimicrobial resistance (AMR) threatens our public health and is mainly driven by antimicrobial usage (AMU). For this reason the World Health Organization calls for detailed monitoring of AMU over all animal sectors involved. Therefore, we aimed to quantify AMU on turkey farms. First, turkey-specific Defined Daily Dose (DDD_turkey) was determined. These were compared to the broiler alternative from the European Surveillance of Veterinary Antimicrobial Consumption (DDD_vet), that mention DDD_vet as a proxy for other poultry species. DDD_turkey ranged from being 81.5% smaller to 48.5% larger compared to its DDD_vet alternative for broilers. Second, antimicrobial treatments were registered on 60 turkey farms divided over France, Germany and Spain between 2014 and 2016 (20 flocks per country). Afterwards, AMU was quantified using treatment incidence (TI) per 100 days. TI expresses the percentage of the rearing period that the turkeys were treated with a standard dose of antimicrobials. Minimum, median and maximum TI at flock level and based on DDD_turkey = 0.0, 10.0 and 65.7, respectively. Yet, a huge variation in amounts of antimicrobials used at flock level was observed, both within and between countries. Seven farms (12%) did not use any antimicrobials. Aminopenicillins, polymyxins, and fluoroquinolones were responsible for 72.2% of total AMU. The proportion of treating farms peaked on week five of the production cycle (41.7%), and 79.4% of the total AMU was administered in the first half of production. To conclude, not all DDD_vet values for broilers can be applied to turkeys. Additionally, the results of AMU show potential for reducing and improving AMU on turkey farms, especially concerning the usage of critically important antimicrobials.

Pharmacokinetics of florfenicol and thiamphenicol after single oral and intravenous, as well as multiple oral administrations to geese

1. This study evaluated the pharmacokinetic profiles of florfenicol (FF) and thiamphenicol (TP), which are synthetic bacteriostatic antimicrobial drugs, in geese after a single intravenous or oral administration, as well as seven oral doses administered at 12 h intervals. For all treatments, the dose was 30 mg/kg. 2. After single IV administration, clearance and volume of distribution were low (0.23 ± 0.03 l/h/kg and 0.57 ± 0.08 l/kg for FF, and 0.23 ± 0.04 l/h/kg and 0.59 ± 0.08 l/kg for TP, respectively). The elimination half-life was similar between products and short (2.91 ± 0.41 and 2.84 ± 0.64 h for FF and TP, respectively). 3. The single oral administration resulted in efficient absorption (bioavailability of 83.15 ± 11.48 for FF and 75.21 ± 19.56% for TP) with high maximal concentrations of 30.47 ± 2.47 and 20.02 ± 3.87 μg/ml for FF and TP, respectively. The area under the curve was 108.36 ± 14.96 and 101.81 ± 26.48 mg×h/l for FF and TP, respectively. 4. For both drugs, the two latter parameters were found to be higher compared to earlier studies on terrestrial birds. This suggested that FF and TP may be efficient in treating infections in geese caused by certain bacteria sensitive to chloramphenicol. 5. Neither drug accumulated in tissues following the oral seven doses and no adverse effects were noted in any treated animals. Thus, the selected FF and TP dosage may be considered as a safe treatment for geese.

Pharmacokinetics of thiamphenicol in Japanese quails (Coturnix japonica) after single intravenous and oral administrations

Thiamphenicol (TP) pharmacokinetics were studied in Japanese quails (Coturnix japonica) following a single intravenous (IV) and oral (PO) administration at 30 mg/kg BW. Concentrations of TP were determined with HPLC and were analyzed by a noncompartmental method. After IV injection, elimination half-life (t_1/2λz ), total body clearance (Cl_tot ) volume of distribution at steady state (V_dss ), and mean residence time (MRT) of TP were 3.83 hr, 0.19 L/hr/kg, 0.84 L/kg, and 4.37 hr, respectively. After oral administration of TP, the peak plasma concentration (C_max ) was 19.81 μg/ml and was obtained at 2.00 hr (t_max ) postadministration. Elimination half-life (t_1/2λz ) and mean absorption time (MAT) were 4.01 hr and 1.56 hr, respectively. The systemic bioavailability following oral administration of TP was 78.10%. TP therapy with an oral dosage of 30 mg/kg BW is suggested for a beneficial clinical effect in quails.

Comparative muscle irritation and pharmacokinetics of florfenicol-hydroxypropyl-β-cyclodextrin inclusion complex freeze-dried powder injection and florfenicol commercial injection in beagle dogs

Florfenicol (FF) is a novel animal-specific amidohydrin broad-spectrum antibiotic. However, its aqueous solubility is extremely poor, far below the effective dose required for veterinary clinic. Thus, FF is often used in large doses, which significantly limits its preparation and application. To overcome these shortcomings, the FF-hydroxypropyl-β-cyclodextrin (FF-HP-β-CD) inclusion complexes were developed using the solution-stirring method. The physical properties of FF-HP-β-CD were characterized. A comparison was conducted between FF and FF-HP-β-CD freeze-dried powder injection of their muscle irritation and the pharmacokinetics. The drug loading and saturated solubility of FF-HP-β-CD at 37 °C were 11.78% ± 0.04% and 78.93 ± 0.42 mg/mL, respectively (35.4-fold compared with FF). Results of scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, and Fourier transform infrared showed that FF was entrapped in the inner cavity of HP-β-CD, and the inclusion complex formed in an amorphous state. In comparison with FF commercial injection, FF-HP-β-CD increased the elimination half-life (t_1/2β), transport rate constant (K₁₀, K₁₂, K₂₁), and maximum concentration (C_max) after intramuscular injection in beagle dogs. Conversely, it decreased the distribution half-life (t_1/2α), absorption rate constant (Ka), apparent volume of distribution (V1/F), and peak time (T_max). These results suggest that FF-HP-β-CD freeze-dried powder injection is a promising formulation for clinical application.

Relevance of Breast Cancer Resistance Protein to Pharmacokinetics of Florfenicol in Chickens: A Perspective from In Vivo and In Vitro Studies

Florfenicol (FFC) is a valuable synthetic fluorinated derivative of thiamphenicol widely used to treat infectious diseases in food animals. The aims of the study were to investigate whether FFC is a substrate for the breast cancer resistance protein (BCRP) and whether the transporter influences oral availability of FFC. In vitro transport assays using MDCK-chAbcg2 cells were conducted to assess chicken BCRP-mediated transport of FFC, while in vivo pharmacokinetic experiments with single or combined BCRP inhibitor gefitinib were employed to study the role of BCRP in oral FFC disposition. According to U.S. Food and Drug Administration (FDA) criteria, FFC was found to be a potential BCRP substrate due to the net efflux ratio being over 2.0 (2.37) in MDCK cells stably transfected with chicken BCRP and the efflux completely reversed by a BCRP inhibitor (Gefitinib). The molecular docking results indicated that florfenicol can form favorable interactions with the binding pocket of homology modeled chicken BCRP. Pharmacokinetic studies of FFC in different aged broilers with different expression levels of BCRP showed that higher BCRP expression would cause a lower Area Under Curve (AUC) and a higher clearance of FFC. In addition, more extensive absorption of florfenicol after the co-administration with gefitinib (a BCRP inhibitor) was observed. The overall results demonstrated that florfenicol is a substrate of the chicken breast cancer resistant protein which in turn affects its pharmacokinetic behavior.

Effect of three polyether ionophores on pharmacokinetics of florfenicol in male broilers

Drug-drug interactions (DDIs) may adversely affect the prevention and cure of diseases. The effects of three polyether ionophore antibiotics, salinomycin (SAL), monensin (MON), and maduramycin (MAD) on the pharmacokinetics of florfenicol (FFC) were investigated in broilers. The chickens were fed rations with or without SAL (60 mg/kg feeds), MON (120 mg/kg feeds), or MAD (5 mg/kg feeds) for 14 consecutive days. FFC was given to the chickens either intravenously (i.v.) or orally (p.o.) at a single dose of 30 mg/kg body weight. Blood samples were taken from each chicken at 0-24 h postadministration of FFC. The plasma concentration of FFC was detected by high-performance liquid chromatography. The plasma concentration of FFC decreased with i.v. or p.o. co-administration of SAL, MON, or MAD in broilers, implying occurrence of DDIs during the co-administration of FFC with these ionophores. Our findings suggest that more attention should be given to the use of FFC to treat bacterial infections in chickens supplemented with polyether ionophore antibiotics.

Occurrence of ciprofloxacin, enrofloxacin, and florfenicol in animal wastewater and water resources

Antimicrobial agent residues are becoming an intractable environmental problem in soil, surface, and underground water. To obtain a broad profile of residues in animal wastewater and surface water, 24 animal wastewater, 8 animal farm effluent, 18 river water, and 8 pond water samples taken in Jiangsu in eastern China were monitored for enrofloxacin, ciprofloxacin, and florfenicol using solid phase extraction and high performance liquid chromatography/electrospray ionization-tandem mass spectrometry (HPLC/ESI-MS/MS) techniques. The results revealed that two antibacterials were detected simultaneously in 49.1% of samples, followed by three antibacterials (22.6%) and one antibacterial (22.6%). Up to 3.35, 5.93, and 2.10 μg L for ciprofloxacin, 1.09, 4.24, and 0.50 μg L for enrofloxacin, and 0.95, 2.40, and 2.84 μg L for florfenicol were detected in animal farm-effluent, river, and pond water, respectively. The maximum concentrations of ciprofloxacin and enrofloxacin in animal wastewaters were 7.49 and 8.77 μg L, respectively. Furthermore, residue levels of ciprofloxacin and florfenicol showed at least two statistical differences between any two sampling areas or two animal farms. Enrofloxacin showed no statistical difference among the sampling areas and the animal farms.