Florfenicol Amine Research Articles

Atmospheric pressure ionization–tandem mass spectrometry of the phenicol drug family

In this work, the mass spectrometry behaviour of the veterinary drug family of phenicols, including chloramphenicol (CAP) and its related compounds thiamphenicol (TAP), florfenicol (FF) and FF amine (FFA), was studied. Several atmospheric pressure ionization sources, electrospray (ESI), atmospheric pressure chemical ionization and atmospheric pressure photoionization were compared. In all atmospheric pressure ionization sources, CAP, TAP and FF were ionized in both positive and negative modes; while for the metabolite FFA, only positive ionization was possible. In general, in positive mode, [M + H](+) dominated the mass spectrum for FFA, while the other compounds, CAP, TAP and FF, with lower proton affinity showed intense adducts with species present in the mobile phase. In negative mode, ESI and atmospheric pressure photoionization showed the deprotonated molecule [M-H](-), while atmospheric pressure chemical ionization provided the radical molecular ion by electron capture. All these ions were characterized by tandem mass spectrometry using the combined information obtained by multistage mass spectrometry and high-resolution mass spectrometry in a quadrupole-Orbitrap instrument. In general, the fragmentation occurred via cyclization and losses or fragmentation of the N-(alkyl)acetamide group, and common fragmentation pathways were established for this family of compounds. A new chemical structure for the product ion at m/z 257 for CAP, on the basis of the MS(3) and MS(4) spectra is proposed. Thermally assisted ESI and selected reaction monitoring are proposed for the determination of these compounds by ultra high-performance liquid chromatography coupled to tandem mass spectrometry, achieving instrumental detection limits down to 0.1 pg.

ESTABLISHMENT OF A COMPETITIVE ELISA FOR DETECTION OF FLORFENICOL ANTIBIOTIC IN FOOD OF ANIMAL ORIGIN

Florfenicol (FF) is a synthetic antibiotic with a broad antibacterial spectrum and the high therapeutic effectiveness that has been developed specifically for veterinary use. Obviously, FF adulterated in animal supplies is one of essential global concerns. A competitive ELISA for the detection of florfenicol in food of animal origin (swine, chicken, and fish) is described. Influence of immunoconjugate structure on the assay sensitivity and specificity was investigated. The new ELISA showed much lower than the MRPLs for FF at 100–3,000 mg kg−1 in the European Communities and the sensitivity of our ELISA method was superior to that described in other reports. According to the test preparation record, the limit of detection of the developed ELISA performed on meat species was 0.3 µg kg−1 (IC50 value 1.9 µg kg−1). The method developed permits FF concentrations to be determined in the range 0.3–24.3 µg kg−1. A low cross-reactivity with florfenicol amine (FFA), thiamphenicol (TAP), and chloramphenicol (CAP) was displayed (16.2%, 9.5%, and 9.4%, respectively). Recovery in different food samples (swine, chicken, and fish) averages between 87–115%. The method can be applied for inspection of animal supplies for trace florfenicol residues.

Pharmacokinetics of Florfenicol after Oral Administration in Yellow Catfish, Pelteobagrus fulvidraco

AbstractThe pharmacokinetics of florfenicol (FF) and its metabolite, florfenicol amine (FFA), were investigated after doses of 10 mg/kg/day were administered orally per os (p.o.) on a single day or on three consecutive days in yellow catfish, Pelteobagrus fulvidraco, raised in water temperatures of 25 C. After a single dose p.o. was administered, the apparent volume of distribution at steady state (Vdss) of FF was computed to be 2.52 L/kg. The Tmax values were in the following order: liver (1.82 h) < kidney (2.26 h) < skin (6.15 h) < muscle (6.32 h) < plasma (7.25 h). These results show that FF and FFA accumulated rapidly in the kidney and liver. The t1/2β values in plasma, muscle, skin, liver, and kidney were 9.63, 15.75, 14.44, 11.55, and 15.75 h, respectively, for FF and 21.66, 15.07, 17.33, 26.65, and 30.13 h, respectively, for FFA. After a single p.o. dose was administered on three consecutive days, the t1/2β values of FF and FFA in skin‐on muscle were 17.12 and 13.55 h, respectively. The total concentrations of FF and FFA in skin‐on muscle 1, 3, and 5 d after the last administration were 3.39, 0.5, and 0.062 µg/g, respectively.

Development of a rapid chemiluminescent ciELISA for simultaneous determination of florfenicol and its metabolite florfenicol amine in animal meat products

A rapid one-step chemiluminescent competitive indirect enzyme-linked immunosorbent assay (CL-ciELISA) for florfenicol (FF) and its major metabolite florfenicol amine (FFA) residues in animal meat products has been developed. The 50% binding inhibition (IC₅₀) values of the method were 0.195 µg kg⁻¹ for FFA and 0.24 µg kg⁻¹ for FF under optimum conditions. The cross-reactive rates for FF and FFA were 100.0% and 81.2%, respectively. FF and FFA were easily extracted from animal meat product with an FF/FFA extraction buffer, obtaining recoveries of 81.8-92.0% (FF) and 77.2-100% (FFA). The whole one-step CL-ciELISA test can be accomplished within 40 min in theory. The detection limits (LODs) of the assay were 0.98 µg kg⁻¹ for FF and 0.80 µg kg⁻¹ for FFA in animal meat samples. Finally, field animal meat samples were analyzed with the CL-ciELISA method, and the results correlated well with those obtained using traditional ELISA and a previously reported liquid chromatographic-tandem mass spectrometric method. The combined results confirmed the utility of this faster one-step CL-ciELISA for simultaneous trace analysis of FF and FFA. To date, this is the most rapid developed ELISA and CL-ELISA method for detection of FF and FFA.

Simultaneous determination of chloramphenicol, florfenicol and florfenicol amine in ham sausage with a hybrid chemiluminescent immunoassay

A novel chemiluminescent immunoassay utilising two types of primary antibodies (murine monoclonal antibody and rabbit polyclonal antibody) and two types of horseradish peroxidase–labelled secondary antibodies was established for simultaneously detecting multiple amphenicol residues in ham sausage. After combining the extract procedure of the target amphenicol into one simplified method, this hybrid chemiluminescent immunoassay could screen chloramphenicol (CAP), florfenicol (FF) and its metabolite florfenicol amine (FFA) at the same time by adding the corresponding secondary antibody. Ham sausage samples were analysed by using this hybrid immunoassay, with LODs of CAP being 0.01 μg kg−1, of FF being 2.8 μg kg−1 and of FFA being 3.0 μg kg−1. The applicability of the proposed method has been validated by determining CAP, FF and FFA in ham sausage samples with satisfactory results. Good recoveries and high correlation with traditional enzyme-linked immunosorbent assay and LC-MS/MS results illustrated that the developed hybrid chemiluminescent immunoassay could screen high-throughput ultra-trace amphenicol residues effectively at one time.

Approaches for the simultaneous detection of thiamphenicol, florfenicol and florfenicol amine using immunochemical techniques

Thiamphenicol and florfenicol are antibacterial agents permitted for use as veterinary drugs in animals used for food production. However, as the EU has established maximum residue limits for both and the metabolite florfenicol amine, there is a requirement to monitor animal food products for their residues. In this study antisera were generated which can simultaneously detect thiamphenicol, florfenicol and florfenicol amine in an immunoassay. Details of the various coupling techniques employed to prepare immunogens and enzyme labels are provided and the antibodies produced have been assessed, in homologous and heterologous ELISA formats, with respect to sensitivity and specificity. It was found that while the antisera raised to thiamphenicol and florfenicol generally performed better in a heterologous set up, those raised to florfenicol amine were not only less affected by the assay format but also produced the most sensitive antibodies to all three target analytes. Antisera matched previous sensitivity (IC50<1ngmL−1) but had improved cross-reactivity (>100%) to thiamphenicol and florfenicol.

Florfenicol depletion in edible tissue of rainbow trout, Oncorhynchus mykiss (Walbaum), and sea bream, Sparus aurata L.

An increase in fish production has consequently brought an increase in infectious diseases in fish farms. The use of chemotherapic drugs is the most effective instrument against common bacterial agents. The number of registered drugs for use in aquaculture is limited and often veterinary practitioners resort to the off-label use of chemotherapic agents authorized for different food-producing animal species. Florfenicol is well known for its outstanding effect against various pathogenic bacteria affecting fish, and therefore, it may be a useful drug for off-label use in aquaculture. The aim of this study was to evaluate the depletion of florfenicol and its major metabolite, florfenicol amine, from the edible tissue of two fish species, rainbow trout and sea bream, following treatment with medicated feed at a dosage of 10mgkg(-1) of bwday(-1) , for 10 consecutive days. At prefixed time points after the end of administration (0.25, 1, 2, 3, 4, 6, 7, 10, 14 and 21days after treatment), edible tissues (muscle plus adherent skin) from 15 individuals in each group were collected and analysed by HPLC, to determine concentration of the drug in the tissue. On the basis of the obtained concentrations, withdrawal times of florfenicol in the two species were calculated. The results indicate that a drug withdrawal time of 500°C-day, as established by Directive 2004/28/EC, for off-label drug use is more than satisfactory to guarantee the healthiness of fish products against the risk of drug residues.

Matrix effects in the simultaneous determination of fenicol antibiotics in swine muscle and casings by ultra performance liquid chromatography-tandem mass spectrometry

Animal tissue samples were extracted with ethyl acetate or alkalized ethyl acetate, and purified with MCX or LC-18 solid-phase extraction columns, and the matrix effects (ME%) in the simultaneous determination of four fenicol antibiotics including chloramphenicol (CAP), thiamphenicol (TAP), florfenicol (FF), and florfenicol amine (FFA) were studied by ultra performance liquid chromatography-tandem mass spectrometry. ME% for FFA in swine muscle and casings extracted by ethyl acetate with LC-18 column cleanup were 11.1% and 10.4%, and in swine muscle extracted by ethyl acetate and alkalized ethyl acetate with MCX column cleanup ME% were 8.1% and 16.1%, respectively, showing strong signal suppression; while ME% for FF in swine muscle extracted by ethyl acetate and alkalized ethyl acetate with LC-18 column cleanup were 148.5% and 146.9%, and in swine muscle extracted by ethyl acetate and alkalized ethyl acetate with MCX column cleanup were 234.3% and 150.9%, showing strong signal reinforcement. Deuterated chloramphenicol-d5 could only be used as an internal standard to eliminate matrix effects for CAP determination. It may be that the most effective method to eliminate matrix interference in the simultaneous determination of the four analytes is quantified by using matrix-matched solutions. Under the optimum conditions of sample pretreatment and quantitative analysis, the decision limits (ccα as specified in European Directive 2002/657/EC) for FFA, TAP, CAP and FF in swine muscle were determined to be 0.4, 0.05, 0.02 and 0.02 μg kg−1, and 0.5, 0.1, 0.04 and 0.03 μg kg−1 in casings; the detection capabilities in swine muscle were determined to be 0.7, 0.09, 0.05 and 0.05 μg kg−1, and 1.2, 0.19, 0.12 and 0.07 μg kg−1 in casings, respectively.

Fate of Florfenicol in a Simulated Aquatic Ecosystem and Effects on Sediment Microflora

Four controlled microcosms were prepared, one of which served as control, whereas the other three received treatments of 10, 50, and 150 mg/L of florfenicol, an antibacterial drug developed initially for aquaculture applications. Water and sediment samples were collected according to a pre-set time schedule to determine its fate in the aquatic environment. The results demonstrated that florfenicol amine was not detectable in any treatment groups. The half-life of florfenicol in pond water was 30.76, 52.92, and 51.48 hours for the 10, 50, and 150 mg/L treatment groups, respectively; the corresponding half-lives in sediment were 25.42, 38.40, and 53.59 days. Further, the 50 and 150 mg/L florfenicol treatment groups inhibited alkaline protease activity; however, all treatment groups inhibited sediment microflora structural diversity.

Study of forced degradation behaviour of florfenicol by LC and LC-MS and development of a validated stability-indicating assay method

A stability-indicating high performance liquid chromatography (HPLC) method was developed for the analysis of florfenicol in presence of its two available identified degradation products (thiamphenicol and chlorfenicol). The drug was subjected to different International Conference On Harmonisation (ICH) prescribed stress conditions (hydrolysis, oxidation and photolysis). The products formed under different stress conditions were investigated by liquid chromatography (LC) and liquid chromatography-mass spectrometry (LC-MS). The LC method involved a Knauwer Eurospher C18 thermostated column at 25°C; and ammonium acetate buffer 6.49mM (pH adjusted to 4.5)-methanol (70:30 v/v) as mobile phase. The flow rate and detection wavelength were 1ml/min and 225nm respectively. The drug showed instability under acidic, alkaline and photolytic stress conditions mainly in solution state form; however, it remains stable in solid state form and under oxidative stress conditions. The developed method was validated for linearity, precision, accuracy and specificity. The degradation products were characterized by LC-MS. Through the mass/ionization (m/z) values and fragmentation patterns, two principal degradation products listed in bibliography have been shown: the florfenicol amine and thiamphenicol. Based on the results, a more complete degradation pathway of the drug could be proposed.

Residue Depletion of Florfenicol and its Metabolite Florfenicol Amine in Eggs

Residue Depletion of Florfenicol and its Metabolite Florfenicol Amine in Eggs

Pharmacokinetics of florfenicol and its metabolite, florfenicol amine, in rice field eel (Monopterus albus) after a single‐dose intramuscular or oral administration

The pharmacokinetics of florfenicol (FF) and its metabolite, florfenicol amine (FFA), were studied in rice field eel (Monopterus albus) after a single dose (20 mg/kg) by intramuscular (i.m.) or oral gavage (p.o.) dose at 25 °C. The elimination half-lives (t1/2β ), peak concentration of FF (Cmax ), and time to reach FF peak concentration (Tmax ) in plasma were estimated as 18.39 h, 10.83 μg/mL, and 7.00 h, respectively, after i.m. injection and 13.46 h, 8.37 μg/mL, and 5 h, respectively, after p.o. administration. The Tmax values of FF in tissues (i.e., kidney, muscle, and liver) were larger for i.m. injection compared with those for p.o. administration. The t1/2β had the following order kidney>muscle>liver for i.m. administrated and kidney>liver>muscle for p.o. administrated. The largest area under the concentration-time curve (AUC) was calculated to be 384.29 mg·h/kg after i.m. dosing, and the mean residence time (MRT) was 42.46 h by oral administration in kidney. FFA was also found in all tissues with a lower concentration than FF for both i.m. and p.o. administrations throughout the study. The elimination of FFA was slow with a t1/2β between 18.19 and 47.80 h in plasma and tissues. The mean metabolic rate of FFA for i.m. and p.o. administrations was >23.30%.

Development and validation of a chemiluminescent ELISA for simultaneous determination of florfenicol and its metabolite florfenicol amine in chicken muscle

A competitive indirect chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA) for florfenicol (FF) and its major metabolite florfenicol amine (FFA) residues in chicken muscle has been developed and validated according to Commission Decision 2002/657/EC criteria. The IC50 value of the method was 0.153 μg kg−1 for FFA with a cross-reactivity of 74.3% for FF under optimum conditions, in which FFA–F–BSA (FFA–formaldehyde–BSA) and FF–G–OVA (FF–glutaric anhydride–OVA) were used as an immunogen and a coating antigen, respectively. FFA and FF were easily extracted from chicken muscle with a 40:1 ethyl acetate–ammonia mixture, obtaining recoveries of 70.3–100% (FFA) and 71.8–102.0% (FF). Accuracy, precision, selectivity, robustness, limit of detection (LOD), limit of quantification (LOQ) and detection capability (CCβ) of the assay have been assessed during the validation process. LOD values in chicken muscle were 0.353 μg kg−1 for FFA and 0.526 μg kg−1 for FF (10-fold dilution) and 0.453 μg kg−1 for FFA and 0.657 μg kg−1 for FF (100-fold dilution). Furthermore, the CL-ELISA method gave CCβ values of 1.0 μg kg−1 for FFA and FF. Finally, real chicken muscle samples were analyzed with the CL-ELISA method, traditional ELISA and a previously reported gas chromatography-negative chemical ionization mass spectrometry (GC-MS), and results confirmed the utility of this new CL-ELISA for trace determination of FF and FFA, simultaneously.

Simultaneous determination of thiamphenicol, florfenicol and florfenicol amine in eggs by reversed-phase high-performance liquid chromatography with fluorescence detection

A specific, sensitive and widely applicable reversed-phase high-performance liquid chromatography with fluorescence detection (RP-HPLC-FLD) method was developed for the simultaneous determination of thiamphenicol (TAP), florfenicol (FF) and florfenicol amine (FFA) in eggs. Samples were extracted with ethyl acetate–acetonitrile–ammonium hydroxide (49:49:2, v/v), defatted with hexane, followed by RP-HPLC-FLD determination. Liquid chromatography was performed on a 5 μm LiChrospher C 18 column using a mobile phase composed of acetonitrile (A), 0.01 M sodium dihydrogen phosphate containing 0.005 M sodium dodecyl sulfate and 0.1% triethylamine, adjusted to pH 4.8 by 85% phosphoric acid (B) (A:B, 35:65 v/v), at a flow rate of 1.0 mL/min. The fluorescence detector of HPLC was set at 224 nm for excitation wavelength and 290 nm for emission wavelength. Limits of detection (LODs) were 1.5 μg/kg for TAP and FF, 0.5 μg/kg for FFA in eggs; limits of quantitation (LOQs) were 5 μg/kg for TAP and FF, 2 μg/kg for FFA in eggs. Linear calibration curves were obtained over concentration ranges of 0.025–5.0 μg/mL for TAP with determination coefficients of 0.9997, 0.01–10.0 μg/mL for FF with determination coefficients of 0.9997 and 0.0025–2.50 μg/mL for FFA with determination coefficients of 0.9998, respectively. The recovery values ranged from 86.4% to 93.8% for TAP, 87.4% to 92.3% for FF and from 89.0% to 95.2% for FFA. The corresponding intra-day and inter-day variation (relative standard deviation, R.S.D.) found to be less than 6.7% and 10.8%, respectively.

Plasma and tissue depletion of florfenicol in olive flounder ( Paralichthys olivaceus) after oral administration

The aim of this study was to evaluate the pharmacokinetics of florfenicol after intravenous (i.v.) and oral (p.o.) administrations and investigate its depletion after multiple oral administrations for 3 consecutive days in olive flounder ( Paralichthys olivaceus). After i.v. injection of 5 mg/kg, the terminal half-life (t 1/2λz), the volume of distribution at steady-states (V ss), and the total body clearance of florfenicol were 38.06 ± 6.10 h, 0.62 ± 0.19 l/kg and 0.012 ± 0.001 l kg/h, respectively. After p.o. administration of 20 mg/kg, the t 1/2λz, C max, T max and oral bioavailability (F) of florfenicol were 51.18 ± 8.03 h, 12.18 ± 3.21 μg/ml, 4 h and 43.00 ± 5.71%, respectively. Florfenicol amine, a major metabolite of florfenicol, was not detected in any samples following p.o. and i.v. administrations of florfenicol in olive flounder and this lack of metabolism may well explain the slower elimination of florfenicol in olive flounder. After multiple oral doses (20 mg/kg/day for 3 days), the prolonged presence of residues in various tissues can play an important role in human food safety and tissue disposition of florfenicol in olive flounder. A withdrawal time of 8 days was necessary to ensure that the residues of florfenicol were less than the maximal residue limit of tolerance established by the European Union.

Differential heat stability of amphenicols characterized by structural degradation, mass spectrometry and antimicrobial activity

Heat stability of amphenicols and the relationship between structural degradation and antimicrobial activity after heating has not been well investigated. Florfenicol (FF), thiamphenicol (TAP), and chloramphenicol (CAP) were heated at 100 °C in water, salt water, soybean sauce and chicken meat for up to 2 h. Degradation and antimicrobial activity of the compounds was evaluated using capillary electrophoresis (CE) with UV-DAD spectrometry, minimum inhibitory concentration (MIC) assay, and gas chromatography with electron impact ionization mass spectrometry (GC–EI-MS). Heat stability of amphenicols in matrices was ranked as water ≥ salt water > soybean sauce > meat, suggesting that heat degradation of amphenicols was accelerated in soybean sauce and was not protected in meat. Heat stability by drug and matrices was ranked as FF > TAP = CAP in water, FF = TAP > CAP in salt water, TAP ≥ FF = CAP in soybean sauce, and TAP ≥ FF = CAP in meat, indicating differential heat stability of amphenicols among the 3 drugs and in different matrices. In accordance with the less than 20% degradation, the MIC against Escherichia coli and Staphylococcus aureus did not change after 2 h heating in water. A 5-min heating of amphenicols in water by microwave oven generated comparable percentage degradation to boiling in water bath for 30 min to 1 h. Both CE and GC–MS analysis showed that heating of FF produced TAP but not FF amine as one of its breakdown products. In conclusion, despite close similarity in structure; amphenicols exhibited differential behavior toward heating degradation in solutions and protein matrices. Although higher degradations of amphenicols were observed in soybean sauce and meat, heating treatment may generate product with antimicrobial activity (FF to TAP), therefore, heating of amphenicol residues in food cannot always be assumed safe.

Depletion of florfenicol amine, marker residue of florfenicol, from the edible fillet of tilapia ( Oreochromis niloticus x O. niloticus and O. niloticus x O. aureus) following florfenicol administration in feed

Aquaflor ®, a 50% feed premix containing the broad spectrum antibacterial agent florfenicol is available globally to control mortality associated with economically significant systemic bacterial diseases of fish. Florfenicol (FFC) is effective in controlling mortality associated with Streptococcus iniae in tilapia Oreochromis sp. when administered in medicated feed at a dose of 15 mg/kg bodyweight (BW)/d for 10 consecutive days. Our objective was to characterize the depletion of the FFC marker residue, florfenicol amine (FFA), from the edible tissue of market-weight Nile tilapia O. niloticus x O. niloticus and hybrid tilapia O. niloticus x O. aureus offered feed medicated with FFC at a nominal dose rate of 15 mg/kg BW/d for 12 days. Near market-weight tilapia were obtained from a commercial tilapia farm, distributed to 2 single pass (one for Nile tilapia and one for hybrid tilapia), flow-through systems and maintained at 27 °C under a 15 h light:9 h dark photoperiod over a 41-d pre-dosing period. During the dosing period, tilapia were offered feed medicated with FFC at a concentration of 1.479 g/kg at 1% BW daily divided in three equal offerings. The initial 10-d dosing period was extended to 12 d because one tank did not consume > 75% of the feed offered during the first two dosing days. The total dose consumed by fish in each of the 2 tanks ranged from 147 to 167 mg/kg. Once during the pre-dose period and on days 1, 2, 4, 7, 14, 21, and 28 of the post-dose period, groups of fish were indiscriminately removed from each tank, measured for weight and length, scaled, filleted, and the skin-on fillets stored at <−70 °C. Frozen fillets were individually homogenized, extracted, and FFA concentration was determined by high-performance liquid chromatography with UV detection. Florfenicol amine is rapidly eliminated from tilapia fillet after withdrawal from medication and depletion followed first-order kinetics with an estimated half-life of 2.32 d. The FFA tolerance limit, calculated as the 99th percentile of the potential residue level at 95% confidence, had depleted to less than the 1 µg/g maximum residue level by 6.14 d after the dosing period.

Simultaneous determination of thiamphenicol, florfenicol and florfenicol amine in swine muscle by liquid chromatography–tandem mass spectrometry with immunoaffinity chromatography clean-up

A rapid and sensitive liquid chromatography–electrospray ionization-tandem mass spectrometry (LC–ESI-MS/MS) method to quantify thiamphenicol (TAP), florfenicol (FF), and florfenicol amine (FFA) in swine muscle is described. An immunoaffinity chromatography (IAC) column based on polyclonal antibodies and protein A-sepharose CL 4B was used to clean-up extracted samples. IAC optimized conditions were found that allowed the IAC to be reused for selective binding of TAP, FF, and FFA. The dynamic column capacity was more than 512 ng/mL of gel after being used for 15 cycles. From fortified swine muscle samples at levels of 0.4–50 ng/g, the average recoveries were 85.2–98.9% with intra- and inter-day variations less than 9.8% and 12.4%, respectively. The limit of quantitation ranged from 0.4 to 4.0 μg/kg.

Simultaneous screening and confirmation of multiple classes of drug residues in fish by liquid chromatography-ion trap mass spectrometry

LC-ion trap mass spectrometry was used to screen and confirm 38 compounds from a variety of drug classes in four species of fish: trout, salmon, catfish, and tilapia. Samples were extracted with acetonitrile and hexane. The acetonitrile phase was evaporated, redissolved in water and acetonitrile, and analyzed by gradient chromatography on a phenyl column. MS 2 or MS 3 spectra were monitored for each compound. Qualitative method performance was evaluated by the analysis over several days of replicate samples of control fish, fish fortified with a drug mixture at 1 ppm, 0.1 ppm and 0.01 ppm, and fish dosed with a representative from each drug class. Half of the 38 drugs were confirmed at 0.01 ppm, the lowest fortification level. This included all of the quinolones and fluoroquinolones, the macrolides, malachite green, and most of the imidazoles. Florfenicol amine, metronidazole, sulfonamides, tetracyclines, and most of the betalactams were confirmed at 0.1 ppm. Ivermectin and penicillin G were only detectable in the 1 ppm fortified samples. With the exception of amoxicillin, emamectin, metronidazole, and tylosin, residue presence was confirmed in all the dosed fish.

PHARMACOKINETICS OF FLORFENICOL IN CHANNEL CATFISH (&lt;I&gt;ICTALURUS PUNCTATUS&lt;/I&gt;)AT DIFFERENT WATER TEMPERATURES

The pharmacokinetics of florfenicol(FF) was investigated with a single doe of 10mg/kg body weight after oral gavage administration in channel catfish(Ictalurus punctatus) at the water temperature of 18℃ and 28℃.Florfenicol and its metabolite Florfenicol Amine(FFA) concentrations in fish plasma were simultaneously determined using high-performance liquid chromatography(HPLC) with UV detection.Pharmacokinetic parameters were calculated by using the 3p97 Practical Pharmacokinetic Program software.The results showed that the kinetics of the drug was found to be temperature dependent.Plasma concentration-time data of florfenicol were best fitted using a one-compartmental open model at both 18℃ and 28℃ water temperature.The kinetic equation were Cplasma=7.921(e-0.036t-e-0.180t) and Cplasma=9.061(e-0.081t-e-0.301t)at 18℃ and 28℃ respectively.The major pharmacokinetic parameters at water temperature of 18℃ and 28℃ were as follows:the absorption half-time(T1/2kα) 3.845h and 2.301h,respectively;the elimination half-time(T1/2ke) 19.118h and 8.519h,respectively;The time point of the maximum plasma concentration(Tp) 11.136h and 5.953h respectively,Peak plasma concentration(Cmax) were 4.074μg/mL and 4.226μg/mL,respectively;Area under curve(AUC) 174.547μg/mL·h and 81.279μg /mL·h,respectively;Mean residence time(MRT) were 27.581h and 12.290h,respectively.Relatively apparent distributed volume V/F(c) were approached that were 1.512L/kg and 1.580L/kg respectively.Florfenicol administration for preventing and controlling bacterial disease of channel catfish which is recommended to be once two days at 18℃ or once a day at 28℃ with a doe of 10mg/kg body weight by oral administration.The main metablite FFA of FF was-not detected in channel catfish plasma sample.