Pharmacokinetics and tolerance of florfenicol in Equidae

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.

Florfenicol urinary excretion and its potential for treating canine urinary tract infections

The canine urinary excretion of florfenicol was evaluated to explore its potential for treating urinary tract infections. Nine healthy male intact purpose-bred Beagles and four healthy client-owned dogs each received a single oral dose of florfenicol 20 mg/kg (300 mg/mL parenteral solution) with food. All voluntary urinations were collected for 12 h. Although florfenicol is reportedly bitter tasting, 7/9 Beagles and 4/4 client-owned dogs completely ingested the florfenicol and were enrolled; salivation (n = 1) and headshaking (n = 3) were observed. The last measured urine florfenicol concentrations were variable: Beagles (0.23-3.19 mcg/mL), Pug (3.01 mcg/mL) English Setter (21.29 mcg/mL), Greyhound (32.68 mcg/mL), and Standard Poodle (13.00 mcg/mL). Urine half-life was similar for the Beagles and the Pug, 0.75-1.39 h, whereas the half-life was 1.70-1.82 h for the English Setter, Greyhound, and Standard Poodle. Larger breed dogs exceeded 8 mcg/mL florfenicol (wild-type cutoff) in their urine at 12 h, whereas the Beagles and Pug had <8 mcg/mL; it is unclear if this is an individual, breed, or size difference. These data suggest oral florfenicol may need to be administered q6-12h for canine urinary tract infections, but further data are needed (more enrolled dogs, multiple-dose regimens) before considering clinical trials or breed-specific differences.

Pharmacokinetics of florfenicol and its metabolite florfenicol amine in the plasma, urine, and feces of fattening male donkeys following single oral administration

Florfenicol (FF) is a commonly used antibacterial agent in animals. We investigated the pharmacokinetics of FF and its metabolite florfenicol amine (FFA) in donkeys. Donkeys were administered FF (30 mg/kg bodyweight, p.o.). Pharmacokinetic parameters were calculated using a non-compartmental model. The FF (FFA) pharmacokinetics parameters were characterized by along elimination half-life (t1/2 kz) of 5.92 h (15.95 h), plasma peak concentration (Cmax) of 0.13 μg/mL (0.08 μg/mL), and the time taken to reach Cmax (Tmax) of 0.68 h (0.72 h). The area under plasma concentration-time curve and mean residence time of FF (FFA) in plasma were 1.31 μg·mL-1·h (0.47 μg·mL-1·h) and 10.37 h (18.40 h), respectively. The t1/2 kz of FF and FFA in urine was 21.93 and 40.26 h, and the maximum excretion rate was 10.56 and 4.03 μg/h reached at 25.60 and 32.20 h, respectively. The respective values in feces were 0.02 and 0.01 μg·h-1 reached at 33.40 h. The amount of FF and FFA recovered in feces was 0.52 and 0.22 μg, respectively. In conclusion, FF (FFA) is rapidly absorbed and slowly eliminated after a single oral administration to donkeys. Compared to FF, FFA was more slowly eliminated. FF (FFA) is mostly excreted through urine.

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.

Coptisine Modulates the Pharmacokinetics of Florfenicol by targeting CYP1A2, CYP2C11 and CYP3A1 in the Liver and P-gp in the Jejunum of Rats: A Pilot Study

1. Coptisine (COP) is the main active ingredient of Coptis chinensis. In Chinese veterinary clinics, Coptis chinensis is commonly used alongside florfenicol to treat intestinal infections. The goal of this study was to investigate the impact of COP co-administration on the pharmacokinetics of florfenicol in rats.2. Male Sprague-Dawley rats were orally administered COP (50 mg/kg BW) or sterile water for 7 consecutive days, followed by a single oral dose of florfenicol (25 mg/kg BW) on the 8^th day. Pharmacokinetics of florfenicol were analyzed using non-compartmental methods, while expression levels of cytochrome P450 (CYP) isoforms in the liver and P-glycoprotein (P-gp) in the jejunum were measured using real-time RT-PCR, Western blot and immunohistochemical analyses.3. Co-administration of COP and florfenicol significantly increased AUC_(0-∞), MRT_(0-∞), and C_max of florfenicol, while CLz/F was significantly decreased. COP down-regulated the expression of CYP1A2, CYP2C11, and CYP3A1 in the liver, as well as P-gp in the jejunum.4. These findings suggest that co-administration of COP with florfenicol alters the pharmacokinetics of florfenicol in rats. The down-regulation of CYP and P-gp expression may contribute to this effect. Therefore, the co-administration of COP with florfenicol may enhance the prophylactic or therapeutic efficacy of florfenicol in veterinary practice.

Maximum levels of cross-contamination for 24 antimicrobial active substances in non-target feed. Part 7: Amphenicols: florfenicol and thiamphenicol

The specific concentrations of florfenicol and thiamphenicol in non-target feed for food-producing animals, below which there would not be an effect on the emergence of, and/or selection for, resistance in bacteria relevant for human and animal health, as well as the specific antimicrobial concentrations in feed which have an effect in terms of growth promotion/increased yield, were assessed by EFSA in collaboration with EMA. Details of the methodology used for this assessment, associated data gaps and uncertainties, are presented in a separate document. To address antimicrobial resistance, the Feed Antimicrobial Resistance Selection Concentration (FARSC) model developed specifically for the assessment was applied. The FARSC for florfenicol was estimated. However, due to the lack of data, the calculation of the FARSC for thiamphenicol was not possible until further experimental data become available. To address growth promotion, data from scientific publications obtained from an extensive literature review were used. Levels in feed that showed to have an effect on growth promotion/increased yield were reported for florfenicol, whilst for thiamphenicol no suitable data for the assessment were available. Uncertainties and data gaps associated to the levels reported were addressed. For florfenicol, it was recommended to perform further studies to supply more diverse and complete data related to the requirements for calculation of the FARSC, whereas for thiamphenicol, the recommendation was to generate the data required to fill the gaps which prevented the FARSC calculation.

Borneol influences the pharmacokinetics of florfenicol through regulation of cytochrome P450 1A2 (CYP1A2), CYP2C11, CYP3A1, and multidrug resistance 1 (MDR1) mRNA expression levels in rats

Borneol is a traditional Chinese medicine. In Chinese veterinary clinics, borneol and its related compounds are often used in combination with florfenicol to treat respiratory infections. This study investigated whether the pharmacokinetics of florfenicol in rats was affected by its concomitant use with borneol. Sprague-Dawley rats were intragastrically administered borneol (50 mg/kg body weight (BW)) or 0.5% carboxymethyl-cellulose sodium for 7 consecutive days, and then intragastrically administered florfenicol (25 mg/kg BW) on the eighth day. Pharmacokinetic studies showed that borneol significantly decreased the area under the concentration-time curve from zero to infinity (AUC_(0-t)), time to reach peak concentration (T_max), and the peak concentration (C_max) values of florfenicol, whereas the values of mean residence time from zero to infinity (MRT_(0-t)), elimination half-life (t_1/2z), apparent volume of distribution fraction of the dose absorbed (Vz), and plasma clearance fraction of the dose absorbed (CLz) were increased significantly. Furthermore, the mRNA expression levels of multidrug resistance 1 (MDR1) and cytochrome P450 3A1 (CYP3A1) in the jejunum and of CYP1A2 and CYP2C11 in the liver were significantly upregulated by borneol. In conclusion, borneol decreased absorption, increased clearance, improved distribution, and increased the mean residence time of florfenicol in rats, possibly through regulating the mRNA expression levels of drug-metabolizing enzymes and efflux transporters.

Alterations in the Fecal Microbiome and Metabolome of Horses with Antimicrobial-Associated Diarrhea Compared to Antibiotic-Treated and Non-Treated Healthy Case Controls

Diarrhea is an adverse effect of antimicrobial therapy in horses. This matched, case-controlled study compared the fecal microbiome and metabolome of horses on antibiotics that developed diarrhea (AAD, n = 17) to those that did not develop diarrhea (ABX, n = 15) and to a control population not exposed to antibiotics (CON, n = 31). Fecal samples were collected from horses that were matched for diet and antimicrobial agent (including dose, route, and duration of therapy). Illumina sequencing of 16S rRNA genes was performed, and QIIME 2.0 was used to generate alpha and beta diversity metrics. Untargeted metabolomics using GC-MS platforms was performed and analyzed using Metaboanalyst 5.0. Microbiome composition was significantly different in AAD compared to CON (ANOSIM, R = 0.568, p = 0.001) but not to ABX (ANOSIM, R = 0.121, p = 0.0012). AAD and ABX horses had significantly decreased richness and evenness compared to CON horses (p < 0.05). Horses on antimicrobials (AAD and ABX) had significant changes in 14 phyla compared to CON horses. Only Verrucomicrobia distinguished AAD from ABX and CON horses (q = 0.0005). Metabolite profiles of horses with AAD clustered separately from ABX and CON horses. Seven metabolites were found to be significantly different between groups (p < 0.05): L-tyrosine, kynurenic acid, xanthurenic acid, 5-hydroxyindole-3-acetic acid, docosahexaenoic acid ethyl ester, daidzein, and N-acetyltyramine. Metabolite profiles of horses on antimicrobials, especially those with AAD, are altered compared to CON horses.

Florfenicol induces renal toxicity in chicks by promoting oxidative stress and apoptosis

To explore the mechanism of renal toxicity induced by florfenicol (FFC), 120 chicks were randomly divided into 6 groups, 20 in each group. Except for the control group, different doses of FFC (0.15 g/L, 0.3 g/L, 0.6 g/L, 1.2 g/L, and 1.8 g/L) were added to drinking water in the other 5 groups. Five days later, blood was collected from the vein under the wing, and the complete kidneys were obtained as soon as possible, then tested the experimental indicators. The results showed that compared with control group, all doses of FFC significantly reduced the average weight gain of chicks (P < 0.05 or P < 0.01). Except for the 0.15 g/L FFC group, kidney index of chicks in the other doses of FFC groups were significantly increased (P < 0.05 or P < 0.01). The kidney tissues in all FFC groups showed obvious damage, deformities, cell atrophy, and cell gap enlargement. In addition, all doses of FFC significantly increased the contents of uric acid (UA), blood urea nitrogen (BUN), creatinine (CRE) in serum, and malondialdehyde (MDA) in renal tissue (P < 0.05 or P < 0.01), but significantly reduced the levels of glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) in renal tissue (P < 0.05 or P < 0.01). FFC significantly inhibited the mRNA and protein expression levels of nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and nicotinamide adenine dinucleotide phosphate: quinone oxidoreductase-1 (NQO-1), and increased the mRNA and protein expression levels of p53, Caspase-3, and Caspase-6 (P < 0.05 or P < 0.01). The apoptotic rate of renal cells in all doses of FFC groups increased significantly (P < 0.05 or P < 0.01). It was concluded that FFC had a certain degree of nephrotoxicity, and with the increase of FFC concentration, the kidney injury of chicks became more and more serious. FFC promoted oxidative stress response in kidney of chicks by inhibiting the expression of related factors in Nrf2-ARE pathway. Moreover, the expression of pro-apoptotic factors was upregulated to improve the apoptosis rate of renal cells, which resulted in excessive apoptosis of renal cells and seriously affected the kidney function of chicks.

Effects of anemoside B4 on pharmacokinetics of florfenicol and mRNA expression of CXR, MDR1, CYP3A37 and UGT1E in broilers

Pulsatillae radix, a traditional Chinese medicine (TCM), is often used in combination with florfenicol for treatment of intestinal infection in Chinese veterinary clinics. Anemoside B4 (AB4) is the major effective saponin in Pulsatillae radix. This study aimed to investigate whether the pharmacokinetics of florfenicol in broilers was affected by the combination of AB4. In this study, broilers were given AB4 (50 mg/kg BW), or 0.9% sodium chloride solution by oral administration for 7 days. They were then fed florfenicol orally (30 mg/kg BW) on the eighth day. The results showed that the AUC_(0-∞), MRT_(0-∞), t_1/2z and C_max of florfenicol were significantly decreased, and the Vz/F and CLz/F were significantly increased by AB4; the mRNA expression levels of CXR, CYP3A37 and MDR1 (except CXR and CYP3A37 in the liver) were up-regulated by AB4. In conclusion, AB4 altered the pharmacokinetics of florfenicol, resulting in lower plasma concentrations of florfenicol, this was probably related to the mRNA expression of CXR, CYP3A37 and MDR1 in the jejunum and liver (except CXR and CYP3A37) increased by AB4. The implications of these findings on the effect of traditional Chinese medicine containing AB4 on the effectiveness of florfenicol in veterinary practice deserve study.

Pharmacokinetic model of florfenicol in turbot (Scophthalmus maximus): establishment of optimal dosage and administration in medicated feed

The pharmacokinetics of florfenicol (FF) in turbot (Scophthalmus maximus) was studied after single intravenous (10 mg kg^-1 ) and oral (100 mg kg^-1 ) administration. The plasma concentration-time data of florfenicol were described by an open one-compartment model. The elimination half-life (t_1/2 ) was estimated to be 21.0 h, and the total body clearance, Cl, was determined as 0.028 L kg h^-1 . The apparent volume distribution (V_d ) was calculated to be 0.86 L kg^-1 and the mean residence time (MRT_iv ) was 30.2 h. Following oral administration, the maximum plasma concentration (C_max ) of 55.4 μg mL^-1 was reached at 12 h (T_max ). The absorption constant (k_a ) was 0.158 h^-1 . The bioavailability was estimated to be 57.1%. The low bioavailability observed at higher doses was explained by the saturation of the mechanisms of absorption. The drug absorption process was limited by its inherent low solubility, which limited the amount of available FF absorbed in the gastrointestinal tract. Based on the pharmacokinetic data, an optimal dosing schedule for FF administration is hereby provided. Based on the minimum inhibitory concentration found for susceptible strains of Aeromonas salmonicida, oral FF administration of first, an initial dose of 30 mg FF kg^-1 , followed by 6 maintenance doses at 18 mg kg^-1 /daily could be effective against furunculosis in turbot.

Impact of therapeutic and high doses of florfenicol on kidney and liver functional indicators in goat

Aim:

The aim of this study was to evaluate the impact of therapeutic and high doses of florfenicol on kidney and liver functional indicators in goat species.

Materials and Methods:

Six mature, healthy goats (combine breed and sex) with average weight 25 kg were selected for this study. The therapeutic (20 mg/kg b.w.) and high doses (40 and 60 mg) of florfenicol were administered for 3 days with 24 h interval. Blood samples were collected at 0, 24, 48, 72, 96, and 120 h following the each administered dose.

Results:

The results showed that the therapeutic dose of florfenicol produced nonsignificant effect on serum urea, creatinine, total protein (TP), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT) and bilirubin on all timings, and increased (p<0.05) the serum glutamic oxaloacetic transaminase (SGOT) and serum glutamate-pyruvate transaminase (SGPT) levels for 48 h. Whereas the high doses of florfenicol (40 and 60 mg) significantly altered the kidney and liver functional indicators in the blood. In contrast with control, the serum urea level was (p<0.01) increased at all timing points. Creatinine values were altered (p<0.01, <0.05) in increasing manner from 24 to 96 h. The high dose of 40 mg decreased the TP (p<0.05) for 72 h and 60 mg persisted same effect (p<0.01) up to 120 h. The indices of ALP, GGT, SGOT, and SGPT were raised (p<0.01, <0.05) at all timings. The bilirubin indexes also (p<0.05) elevated from 48 to 72.

Conclusion:

It was concluded that the high doses of florfenicol produced reversible dose-dependent effects on functional indicators of kidney and liver such as urea, creatinine, TP, ALP, SGOT, SGPT, GGT, and bilirubin.

Pharmacokinetics of a florfenicol-tylosin combination after intravenous and intramuscular administration to beagle dogs

A pharmacokinetic study of a commercial florfenicol-tylosin (2:1) combination product was conducted in six beagle dogs after intravenous (IV) and intramuscular (IM) administration at doses of 10 mg/kg (florfenicol) and 5 mg/kg (tylosin). Serum drug concentrations were determined by a validated high performance liquid chromatography (HPLC) using UV detection. A rapid and nearly complete absorption of both drugs with a mean IM bioavailability of 103.9% (florfenicol) and 92.6% (tylosin), prolonged elimination half-life, and high tissue penetration with steady state volume of distribution of 2.63 l/kg (florfenicol) and 1.98 l/kg (tylosin) were observed. Additional studies, including pharmacodynamic and toxicological evaluation are required before recommendations can be made regarding the clinical application of the product in dogs.

Plasma and tissue depletion of florfenicol and florfenicol-amine in chickens

Chickens were used to investigate plasma disposition of florfenicol after single intravenous (i.v.) and oral dose (20 mg kg-1 body weight) and to study residue depletion of florfenicol and its major metabolite florfenicol-amine after multiple oral doses (40 mg kg-1 body weight, daily for 3 days). Plasma and tissue samples were analyzed using a high-performance liquid chromatography (HPLC) method. After i.v. and oral administration, plasma concentration-time curves were best described by a two-compartment open model. The mean [ +/- standard deviation (SD)] elimination half-life (t1/2beta) of florfenicol in plasma was 7.90 +/- 0.48 and 8.34 +/- 0.64 h after i.v. and oral administration, respectively. The maximum plasma concentration was 10.23 +/- 1.67 microg mL-1, and the interval from oral administration until maximal concentration was 0.63 +/- 0.07 h. Oral bioavailability was found to be 87 +/- 16%. Florfenicol was converted to florfenicol-amine. After multiple oral dose (40 mg kg-1 body weight, daily for 3 days), in kidney and liver, concentrations of florfenicol (119.34 +/- 31.81 and 817.34 +/- 91.65 microg kg-1, respectively) and florfenicol-amine (60.67 +/- 13.05 and 48.50 +/- 13.07 microg kg-1, respectively) persisted for 7 days. The prolonged presence of residues of florfenicol and florfenicol-amine in edible tissues can play an important role in human food safety, because the compounds could give rise to a possible health risk. A withdrawal time of 6 days was necessary to ensure that the residues of florfenicol were less than the maximal residue limits or tolerance established by the European Union.

Pharmacokinetics of florfenicol and its metabolite, florfenicol amine, in dogs

A study on the bioavailability and pharmacokinetics of florfenicol was conducted in six healthy dogs following a single intravenous (i.v.) or oral (p.o.) dose of 20 mg kg(-1) body weight (b.w.). Florfenicol concentrations in serum were determined by a high-performance liquid chromatography/mass spectrometry. Plasma concentration-time data after p.o. or i.v. administration were analyzed by a non-compartmental analysis. Following i.v. injection, the total body clearance was 1.03 (0.49) L kg(-1)h(-1) and the volume of distribution at steady-state was 1.45 (0.82) L kg(-1). Florfenicol was rapidly distributed and eliminated following i.v. injection with 1.11 (0.94)h of the elimination half-life. After oral administration, the calculated mean C(max) values (6.18 microg ml(-1)) were reached at 0.94 h in dogs. The elimination half-life of florfenicol was 1.24 (0.64) h and the absolute bioavailability (F) was achieved 95.43 (11.60)% after oral administration of florfenicol. Florfenicol amine, the major metabolite of florfenicol, was detected in all dogs after i.v. and p.o. administrations.

Pharmacokinetics of florfenicol, thiamphenicol, and chloramphenicol in turkeys

The pharmacokinetics of florfenicol (FF), thiamphenicol (TP) and chloramphenicol (CP) after single intravenous (i.v.) or oral (p.o.) administration was studied in an independent cross-over study in broiler turkeys. All the fenicol antibiotics were administered at a dose of 30 mg/kg b.w. and their concentrations in plasma samples were assayed using the same validated high-performance liquid chromatography method. Pharmacokinetic parameters were calculated by a noncompartmental method. The kinetic profiles of the compounds were compared with the results of the structure-activity relationship. According to the proposed mathematical description, no differences in plasma clearance values for the studied antibiotics were observed. The mean residence time values of FF, TF, and CP after i.v. injection were 3.37+/-0.63, 2.43+/-0.29, and 2.12+/-0.21 h, respectively. The mean values of Varea for FF (1.39+/-0.31 L/kg) and TP (1.31+/-0.19 L/kg) were similar, but significantly different from that of CP (1.04+/-0.12 L/kg). The bioavailabilities of FF, TP, and CP after oral administration were 82%, 69%, and 45%, respectively. Differences in the bioavailability values of the compared fenicol antibiotics correspond to the ratio of the apolar/polar surface areas of their particles.

Pharmacokinetics of florfenicol and its major metabolite, florfenicol amine, in rabbits

The pharmacokinetics of florfenicol and its active metabolite florfenicol amine were investigated in rabbits after a single intravenous (i.v.) and oral (p.o.) administration of florfenicol at 20 mg/kg bodyweight. The plasma concentrations of florfenicol and florfenicol amine were determined simultaneously by an LC/MS method. After i.v. injection, the terminal half-life (t(1/2lambdaz)), steady-state volume of distribution, total body clearance and mean residence time of florfenicol were 0.90 +/- 0.20 h, 0.94 +/- 0.19 L/kg, 0.63 +/- 0.06 L/h/kg and 1.50 +/- 0.34 h respectively. The peak concentrations (C(max)) of florfenicol (7.96 +/- 2.75 microg/mL) after p.o. administration were observed at 0.90 +/- 0.38 h. The t(1/2lambdaz) and p.o. bioavailability of florfenicol were 1.42 +/- 0.56 h and 76.23 +/- 12.02% respectively. Florfenicol amine was detected in all rabbits after i.v. and p.o. administration. After i.v. and p.o. administration of florfenicol, the observed Cmax values of florfenicol amine (5.06 +/- 1.79 and 3.38 +/- 0.97 microg/mL) were reached at 0.88 +/- 0.78 and 2.10 +/- 1.08 h respectively. Florfenicol amine was eliminated with an elimination half-life of 1.84 +/- 0.17 and 2.35 +/- 0.94 h after i.v. and p.o. administration respectively.

Pharmacokinetics and bioavailability of florfenicol following intravenous, intramuscular and oral administrations in rabbits

This study examined the disposition kinetics and bioavailability of florfenicol after intravenous (i.v.), intramuscular (i.m.) and oral administration to rabbits at a dose of 30 mg/kg BW. Serial blood samples were collected through an indwelling catheter intermittently for 24 h for various routes. Plasma antibacterial concentrations were determined using a microbiological assay method with Bacillus subtilis ATCC 6633 as a reference organism. Plasma concentration-time data generated in the present study were analysed by non-compartmental methods based on statistical moment theory. Following i.v. administration, the overall elimination half-life (t1/2beta) was 1.54 h, mean residence time (MRT) was 1.69 h, mean volume of distribution at steady-state (Vdss) was 0.57 L/kg, and total body clearance (Cltot) was 0.34 L/kg/h. After i.m. and oral dosing, the terminal part of the curve should correspond to the absorption phase, instead of to the elimination phase, with terminal half-lives of 3.01 and 2.57 h, respectively. The mean absorption time (MAT) was 2.65 h for i.m. and 2.01 h for oral administration. Elimination rate constants differed with i.v., i.m. and oral administrations, suggesting a flip-flop situation. The observed mean peak plasma concentrations (Cmax obs) were 21.65 and 15.14 microg/ml achieved at a post-injection time (Tmax obs) of 0.5 h following i.m. and oral dosing, respectively. The absolute systemic availabilities were 88.25% and 50.79%, respectively, and the extent of plasma protein binding percent was 11.65%.

Bioavailability and pharmacokinetics of florfenicol in healthy sheep*

A study on bioavailability and pharmacokinetics of florfenicol was conducted in 20 crossbred healthy sheep following a single intravenous (i.v.) and intramuscular (i.m.) doses of 20 and 30 mg/kg body weight (b.w.). Florfenicol concentrations in serum were determined by a validated high-performance liquid chromatography method with UV detection at a wavelength of 223 nm in which serum samples were spiked with chloramphenicol as internal standard. Serum concentration-time data after i.v. administration were best described by a three-compartment open model with values for the distribution half-lives (T(1/2alpha)) 1.51 +/- 0.06 and 1.59 +/- 0.10 h, elimination half-lives (T(1/2beta)) 18.83 +/- 6.76 and 18.71 +/- 1.85 h, total body clearance (Cl(B)) 0.26 +/- 0.03 and 0.25 +/- 0.01 L/kg/h, volume of distribution at steady-state (V(d(ss))) 1.86 +/- 0.11 and 1.71 +/- 0.20 L/kg, area under curve (AUC) 76.31 +/- 9.17 and 119.21 +/- 2.05 microg.h/mL after i.v. injections of 20 and 30 mg/kg b.w. respectively. Serum concentration-time data after i.m. administration were adequately described by a one-compartment open model. The pharmacokinetic parameters were distribution half-lives (T(1/2k(a) )) 0.27 +/- 0.03 and 0.25 +/- 0.09 h, elimination half-lives (T(1/2k(e) )) 10.34 +/- 1.11 and 9.57 +/- 2.84 h, maximum concentrations (C(max)) 4.13 +/- 0.29 and 7.04 +/- 1.61 microg/mL, area under curve (AUC) 67.95 +/- 9.61 and 101.95 +/- 8.92 microg.h/mL, bioavailability (F) 89.04% and 85.52% after i.m. injections of 20 and 30 mg/kg b.w. respectively.

Comparative plasma pharmacokinetics and tolerance of florfenicol following intramuscular and intravenous administration to camels, sheep and goats

Florfenicol, a monofluorinated analogue of thiamphenicol, has a broad antibacterial spectrum. The pharmacokinetics of florfenicol was studied following a single intravenous (i.v.) or intramuscular (i.m.) injection at a dose of 20 mg/kg body weight in healthy male camels, sheep and goats. The concentration of florfenicol in plasma was determined using a microbiological assay. Pharmacokinetic analysis was performed using a two-compartment open model. Following i.m. administration, the maximum plasma concentration of florfenicol (Cmax) reached in camels, sheep and goats was 0.84 +/- 0.08, 1.04 +/- 0.10 and 1.21 +/- 0.10 microg/ml, respectively, the the time required to reach Cmax (t(max)) in the same three respective species was 1.51 +/- 0.14, 1.44 +/- 0.10 and 1.21 +/- 0.10 h. The terminal half-life (t(1/2)beta) and the fraction of the drug absorbed (F%) in camels, sheep and goats were 151.3 +/- 16.33, 137.0 +/- 12.16 and 127.4 +/- 11.0 min, and 69.20% +/- 7.8% , 65.82% +/- 6.7% and 60.88% +/- 5.9%, respectively. The MRT in the same three respective species was 4.01 +/- 0.45, 3.42 +/- 0.39 and 2.98 +/- 0.32 h. Following i.v. administration, the terminal half-life (t(1/2)beta) and total body clearance (Clbeta) in camels, sheep and goats were 89.5 +/- 9.2, 78.8 +/- 8.3 and 71.1 +/- 8.9 min and 0.33 +/- 0.04, 0.30 +/- 0.03 and 0.27 +/- 0.03 L/h per kg, respectively. The area under the curve (AUC(0-infinity)) and the mean residence time (MRT) in the same three respective species were 60.61 +/- 6.98, 62.45 +/- 6.56 and 74.07 +/- 7.85 microg/ml per h, and 2.71 +/- 0.31, 2.34 +/- 0.25 and 2.11 +/- 0.23 h. These data suggest that sheep and goats absorb and clear florfenicol to a broadly similar extent, but the rate and extent of absorption of the drug tends to be higher in camels. Drug treatment caused no clinically overt adverse effects. Plasma enzyme activities and metabolites indicative of hepatic and renal functions measured 1, 2, 4 and 7 days following the drug treatment were within the normal range, indicating that the drug is safe at the dose used.

Antimicrobial therapy for gastrointestinal diseases

Antibiotics will always be needed in horses for many types of infections, but the adverse consequences also must be considered. For the conditions described in this article, there is justification for antibiotic therapy. The intestinal problems that antibiotics can induce are among the risks from their administration to horses. Disruption of the endogenous bacterial population, colitis, and diarrhea are the most common complications from antibiotic therapy.

Bioavailability and pharmacokinetics of florfenicol in broiler chickens

The bioavailability and pharmacokinetic disposition of florfenicol in broiler chickens were investigated after intravenous (i.v.), intramuscular (i.m.) and oral administrations of 15 and 30 mg/kg body weight (b.w.). Plasma concentrations of florfenicol were determined by a high performance liquid chromatographic method in which plasma samples were spiked with chloramphenicol as internal standard. Plasma concentration-time data after i.v. administration were best described by a two-compartment open model. The elimination half-lives were 168 +/- 43 and 181 +/- 71 min, total body clearance 1.02 +/- 0.17 and 1.02 +/- 0.16 L x kg/h, the volume of distribution at steady-state 4.99 +/- 1.11 and 3.50 +/- 1.01 L/kg after i.v. injections of 15 and 30 mg/kg b.w., respectively. Plasma concentration-time data after i.m. and oral administrations were adequately described by a one-compartment model. The i.m. bioavailability and the oral bioavailability of florfenicol were 95, 98 and 96, 94%, respectively, indicating that florfenicol was almost absorbed completely after i.m. and oral administrations of 15 and 30 mg/kg b.w.

Disposition kinetics of florfenicol in goats by using two analytical methods

Florfenicol, a monofluorinated analogue of thiamphenicol, has antibacterial activity against a broad spectrum of bacterial strains, including enteric bacteria that are resistant to chloramphenicol and thiamphenicol. The pharmacokinetics of florfenicol was studied following a single intravenous bolus or intramuscular injections at a dose of 20 mg/kg body weight, in five healthy goats. Serum florfenicol concentrations were determined using two analytical methods: microbiological assay and high-performance liquid chromatography (HPLC). Pharmacokinetic analysis was performed using redundant routine equations and the results derived from each method were compared. While florfenicol was detected for up to 4 and 8 h after administration by the bioassay, the drug was recovered in serum after 12 and 24 h by HPLC following intravenous and intramuscular injections, respectively. Comparison of the concentration profiles obtained by the two methods revealed substantial differences in the resultant kinetic data. Values for the initial serum concentration, elimination half-life, the area under the serum concentration-time curve, the mean residence time, and the systemic bioavailability were significantly (P < 0.01) higher when florfenicol concentrations were determined using HPLC. In conclusion, differences between analytical methodologies should be considered when interpreting the kinetic data for clinical use. However, both the hepatic biotransformations and the interchangeability of enantiomers need further investigation.

Pharmacokinetics of florfenicol after treatment of pigs with single oral or intramuscular doses or with medicated feed for three days

The pharmacokinetics of florfenicol, a structural analogue of thiamphenicol, were studied in six pigs after single oral and intramuscular doses of 15 mg/kg bodyweight, and after feeding them with medicated feed containing 250 mg/kg for three days, a concentration which provided approximately the same dose rate of the drug. The oral doses contained a specially prepared pelleted formulation of the drug. The bioavailability of the drug was similar for the oral and intramuscular doses. Florfenicol was absorbed rapidly from the feed and its concentration in plasma remained between 2 and 6 microg/ml - above the minimum inhibitory concentration values for common pig pathogens - during the three days.