Treatment of vibriosis in European sea bass larvae, Dicentrarchus labrax L., with oxolinic acid administered by bath or through medicated nauplii of Artemia franciscana (Kellogg): efficacy and residual kinetics.

European sea bass larvae were challenged by bath with Listonella anguillarum strain 332A, 2.5×10(7) CFUmL(-1) for 1h. Fish either received no treatment or oral treatment with Artemia franciscana (Kellog) nauplii enriched with oxolinic acid, or bath treatments with oxolinic acid. Medication commenced 1day following challenge and was performed on days 1, 3 and 5 post-challenge at a dosage of 20mgL(-1) for 2h for bath treatments, while two doses each of 750 nauplii per fish were administered daily for five consecutive days in oral treatments. Cumulative mortality reached 96% for the unmedicated challenged group, 32% in the group receiving bath treatments and 17% in the group receiving medicated nauplii. Pharmacokinetic parameters of oxolinic acid were calculated in sea bass larvae, for both treatments. Steady-state concentrations of oxolinic acid of 48.0 and 75.2µgg(-1) were achieved for bath treatment and oral treatment, respectively, while the elimination half-life was calculated to be 25.1h for bath treatment and 21.7h for oral treatment.

Potential drug (oxytetracycline and oxolinic acid) pollution from Mediterranean sparid fish farms.

The potential for input of two common antibacterial agents in Mediterranean fish farms, oxytetracycline (OTC) and oxolinic acid (OA), was estimated from measurements of these drugs in the faecal excretions of two important farmed sparids, gilthead sea bream, Sparus aurata and sharpsnout sea bream Diplodus puntazzo. Oxolinic acid was found to be well absorbed by gilthead sea bream (92%) and sharpsnout sea bream (88%) while the absorption of OTC was found to be considerably lower in both species (27 and 40%, respectively). These data were integrated with production records for sparids, drug dosage regimes and treatment frequency information to calculate potential annual drug release to the aquatic environment from Greek fish farms. These calculations suggest potentially significant quantities of unmetabolised OTC can be passed unabsorbed through the body of treated sparids and excreted via the faeces into the local marine environment. The situation with OA was much less pronounced. It was estimated that potentially more than 1900 kg of OTC and more than 50 kg of OA may be released via faecal excretion into the environment by sparid farms per year. Further drug may also be released via uneaten medicated feed, leached drugs and other routes of fish elimination (renal excretion, branchial secretions). Drug pollution of the marine environment in the vicinity of fish farms can have adverse ecological effects, including development of resistant bacterial populations and exposure with potential drug accumulation in aquatic fauna and flora.

The bryophyte Fontinalis antipyretica Hedw. bioaccumulates oxytetracycline, flumequine and oxolinic acid in the freshwater environment.

In recent years, the fate of pharmacological substances in the aquatic environment have been more and more studied. Oxolinic acid (OA), flumequine (FLU) and oxytetracycline (OTC) are commonly used antibacterial agents. A large amount of these drugs is released into water directly by dissolved fraction and indirectly in urine and feces. Monitoring these compounds in the freshwater environment is difficult because of the lack of suitable indicators. The aim of this work was to evaluate the OA, FLU and OTC bioaccumulation abilities of Fontinalis antipyretica Hedw., known for heavy metal bioaccumulation. The experiment described was decomposed for two times: a 10-days accumulation period during which bryophytes were in contact with antibiotics and a 15-days post-exposure period during which bryophytes were in water with no antibiotic. This experiment showed that this bryophyte strongly accumulates OA, FLU and OTC in freshwater. Bioaccumulation factors (ratio of concentrations in bryophyte and water) ranged between 75 and 450. Moreover, OA, FLU and OTC persisted in the bryophyte for a long time with clearance between 0.19 and 3.04 ng/g/day. Mean residence times ranged between 18 and 59 days. Accumulation and decontamination mechanism models were proposed.

Experimental study on the bioaccumulation of oxytetracycline and oxolinic acid by the blue mussel (Mytilus edulis). An evaluation of its ability to bio-monitor antibiotics in the marine environment.

The ability of blue mussel (Mytilus edulis) to act as a potential antibiotic bioindicator in marine waters was experimentally tested by the study of the kinetics of two veterinary antibiotics (oxolinic acid: OA and oxytetracycline: OTC). Antibiotic uptake was fast in the soft parts of the mussels. OA was quickly eliminated while OTC was released more slowly (half-life in viscera=3.9 days). OA and OTC were preferentially accumulated in gills and in viscera, respectively. Bio-accumulation factors were low (maximum: 2 for OTC in viscera) in accordance with the low K(ow)s. It was assumed that the higher OTC bioaccumulation pattern was related to its binding to mineral and organic compounds that led to its activity inhibition (62%). The antibiotics were persistent in shells (OTC half-life=8.3 days). Most veterinary and human antibiotics such as tetracyclines and sulphonamides have low log K(ow)(<2) and should weakly accumulate in mussel. This might limit the use of blue mussel to bio-monitor antibiotics in the marine environment.

A single-dose pharmacokinetic study of oxolinic acid and vetoquinol, an oxolinic acid ester, in cod, Gadus morhua L., held in sea water at 8 degrees C and in vitro antibacterial activity of oxolinic acid against Vibrio anguillarum strains isolated from diseased cod.

The pharmacokinetic properties of the antibacterial agent oxolinic acid and vetoquinol, the carbitol ester of oxolinic acid, were studied after intravenous (i.v.) and oral (p.o.) administration to 100-150 g cod, Gadus morhua L., held in sea water at 8 degrees C. Following i.v. injection, the plasma drug concentration-time profile showed two distinct phases. The distribution half-life (t1/2alpha) was estimated at 1.3 h, the elimination half-life (t1/2beta) as 84 h and the total body clearance (Cl(T)) as 0.047 L kg(-1) h(-1). The volume of distribution at steady state, Vd(ss) was calculated to be 5.5 L kg(-1), indicating good tissue penetration of oxolinic acid in cod. Following p.o. administration of oxolinic acid or vetoquinol, the peak plasma concentrations (C(max)) of oxolinic acid and the time to peak plasma concentrations (T(max) were estimated to be 1.2 and 2.5 microg mL(-1) and 24 and 12 h, respectively. The bioavailabilities of oxolinic acid following p.o. administration of oxolinic acid and vetoquinol were calculated to be 55 and 72%, respectively. The in vitro minimum inhibitory concentration (MIC) values of oxolinic acid against three strains of Vibrio anguillarum isolated from diseased cod were 0.016 microg mL(-1) (HI-610), 0.250 microg mL(-1) (HI-618) and 0.250 microg mL(-1) (HI-A21). Based on a MIC value of 0.016 microg mmL(-1) a single p.o. administration of 25 mg kg(-1) of oxolinic acid maintains plasma levels in excess of 0.064 microg mL(-1), corresponding to four times the MIC-value, for approximately 12 days. The analogous value for a single p.o. dose of 25 mg kg(-1) of oxolinic acid administered as vetoquinol was 13 days.

The effect of soybean oil refuse powder used as vehicle on the absorption of oxolinic acid in chickens under fasting and nonfasting conditions and the correlation with in vitro dissolution.

The effect of soybean oil refuse powder (SOR) when used as a vehicle on the absorption of oxolinic acid (OXA) powder in chicken, the dissolution profile of OXA and the correlation between in vivo and in vitro study were examined. To examine in vivo bioavailability, chickens fed or fasted were studied using a 2 x 2 crossover design. The OXA was administered OXA or OXA-SOR (1 : 9) mixture 20 mg OXA/kg. In vitro dissolution rates for OXA and OXA-SOR were measured using the paddle (PD) and the rotatory dialysis cell dissolution (PTSW) methods. Maximum plasma concentration (Cmax) and area under the curve (AUC) were significantly increased by the addition of SOR to OXA. Differences between OXA and OXA-SOR were more remarkable under fasted as compared with fed condition. In vitro dissolution rates of OXA-SOR pH 1.2, 6.5 and 7.2 as determined by the PD and the PTSW methods were increased in the presence of SOR vehicle. Differences between OXA and OXA-SOR in vitro dissolution rates were greater than in vivo bioavailability. Correlation between in vitro release (%) and in vivo absorption (%) showed good linearity (gamma=0.8805-0.9999).

Absorption, tissue distribution and excretion of flumequine and oxolinic acid in corkwing wrasse (Symphodus melops) following a single intraperitoneal injection or bath treatment.

The pharmacokinetic properties of the antibacterial agents oxolinic acid and flumequine were studied in corkwing wrasse (Symphodus melops) after either intraperitoneal injection or bath treatment. Following intraperitoneal administration the peak plasma concentrations (Cmax) and the time to peak plasma concentrations (Tmax) were estimated to be 2.0 microg/mL and 12 h, respectively, for oxolinic acid and 2.6 microg/mL and 12 h, respectively, for flumequine. In muscle, Cmax and Tmax were estimated to 6.7 microg/g and 12 h, respectively, for oxolinic acid with corresponding values of 8.5 microg/g and 13 h, respectively, for flumequine. In liver, Cmax and Tmax were calculated to 7.0 microg/g and 12 h, respectively, for oxolinic and 12.2 microg/g and 11 h, respectively, for flumequine. Elimination half-lives (t1/2 beta) of 26, 24 and 29 h, respectively, for plasma, muscle and liver were calculated for flumequine. For oxolinic acid two distinct elimination phases were found and calculated to be 16 h (t1/2 beta) and 57 h (t1/2 gamma) in plasma, 15 and 59 h, respectively, in muscle and 20 and 72 h, respectively, in liver. Bath treatment using 150 mg/L of flumequine or 200 mg/L of oxolinic acid for 72 h resulted in flumequine concentrations of 1.0 microg/mL in plasma, 5.0 microg/g in muscle and 12.4 microg/g in liver. Corresponding values for oxolinic acid were 1.0 microg/g in plasma, 2.5 microg/g in muscle and 4.9 microg/g in liver.

Elimination of oxolinic acid in eggs after oral treatment of laying hens.

1. Oxolinic acid is often used in poultry as a therapeutic agent. The aim of this study was to determine both its elimination into eggs, following oral dosing through the drinking water (12 mg/kg/d) or diet (13 mg/kg/d) for 5 d and its plasma concentrations. 2. Samples (albumen, yolk, plasma) were analysed by high performance liquid chromatography (HPLC) with fluorimetric detection. The limits of quantification were 10 ng/g in plasma and 5 ng/g in albumen and yolk. Residues were much higher in albumen than in plasma, whereas they were lower in yolk. 3. 95% of the overall oxolinic acid detected in eggs was concentrated in the albumen. 4. Detectable residues persisted for 9 d and 7 d, respectively, in albumen and yolk after the treatment was discontinued.

Pharmacokinetics of a discontinuous absorption process of oxolinic acid in turbot, Scophthalmus maximus, after a single oral administration.

1. The pharmacokinetics of oxolinic acid have been studied in 500 g turbot (Scophthalmus maximus). The fish were kept in seawater at 16 degrees C with a 15 h/9 h photoperiod. Oxolinic acid was administered orally via a stomach tube at a single dose of 10 mg/kg of body weight. Serum concentrations of oxolinic acid were determined by a (HPLC) using liquid phase extraction with an internal standard and a fluorescence detection. 2. The pharmacokinetic process was not significantly sex-influenced. The short elimination phase of the oxolinic acid in turbot after oral administration was similar to the elimination after intravascular administration. The serum concentration profile of oxolinic acid was better described by a discontinuous absorption model than by compartment models using continuous absorption processes. The absorption of oxolinic acid in turbot was characterized by two distinct phases after a lag time of about 2 h. A time (Tmax) of 12 h was necessary to reach the peak serum concentration (Cmax) of 1.41 microg/ml. The oral bioavailability was 27.9%. 3. Based on the minimum inhibitory concentration for susceptible strains, and especially Vibrio anguillarum, the oxolinic acid could be effective in turbot after an oral treatment of 10 mg/kg/day.

Pharmacokinetics of oxolinic acid in sea-bass, Dicentrarchus labrax (L., 1758), after a single rapid intravascular injection.

The pharmacokinetics of oxolinic acid was studied in sea-bass (Dicentrarchus labrax). The fish were kept in seawater at 15.2 degrees C with a 12 h/12 h photoperiod. Oxolinic acid was injected in the caudal vein of anaesthetized sea-bass in a single rapid intravascular administration at a dose of 10 mg/kg of body weight. Plasma concentrations of oxolinic acid were determined using two analytical methods, a classic plate diffusion bioassay using Escherichia coli and a high performance liquid chromatography (HPLC) using solid phase extraction with an internal standard and a U.V. detection. The mean recoveries were 99.6% and 110.8% and determination limits were 0.04 microg/mL and 0.02 microg/mL, for the bioassay and the HPLC respectively. Compared to other fish species, the oxolinic acid was rapidly (absorption half life, t(a1/2) = 0.69 h) distributed to body tissues outside the blood volume (volume of central compartment, Vc = 0.4 L/kg) and presented a large volume of distribution (Vdss = 2.55 L/kg). Considering its disappearance from the central compartment (rate constant: central-eliminated, k10 = 0.16 h[-1]) and its total body clearance (Cl[t] = 0.066 L/kg x h), the elimination phase of the oxolinic acid in sea-bass was shorter than in trout kept in freshwater, and longer than in salmon in seawater. Consequently, the area under the concentration-time curve (AUC = 157 microg x h/mL) and the mean residence time (MRT = 42 h) were relatively low and short, respectively.

Comparative single-dose pharmacokinetics of four quinolones, oxolinic acid, flumequine, sarafloxacin, and enrofloxacin, in Atlantic salmon (Salmo salar) held in seawater at 10 degrees C.

Quinolones are currently the most commonly used group of antimicrobial agents in Norwegian aquaculture. The aims of this study were to examine and compare the pharmacokinetic properties of the quinolones oxolinic acid, flumequine, sarafloxacin, and enrofloxacin after intravascular and oral administration to Atlantic salmon (Salmo salar) by using identical experimental designs. The study was performed in seawater at 10.2 +/- 0.2 degree C with Atlantic salmon weighing 240 +/- 50 g (mean +/- standard deviation). The bioavailability varied considerably among the four quinolones. Following oral administration of medicated feed, the bioavailabilities of oxolinic acid, flumequine, sarafloxacin, and enrofloxacin were 30.1, 44.7, 2.2, and 55.5%, respectively. Taking the different dosages (25 mg/kg of body weight for oxolinic acid and flumequine and 10 mg/kg for sarafloxacin and enrofloxacin) into account, enrofloxacin showed the highest maximum concentration in plasma, followed by flumequine, oxolinic acid, and sarafloxacin. Following intravenous administration, the volumes of distribution at steady state of oxolinic acid, flumequine, sarafloxacin, and enrofloxacin were 5.4, 3.5, 2.3, and 6.1 liters/kg, respectively. Hence, all the quinolones showed good tissue penetration in Atlantic salmon. The elimination half-life of three of the quinolones, oxolinic acid, flumequine, and sarafloxacin, was less than or equal to 24 h, with oxolinic acid showing the shortest (18.2 h). On the other hand, the elimination half-life of enrofloxacin was estimated to be 34.2 h, almost twice that of oxolinic acid. This study showed that flumequine and enrofloxacin had better pharmacokinetic properties, compared with those of oxolinic acid, in Atlantic salmon held in seawater.

Pharmacokinetics, bioavailability, plasma protein binding and disposition of nalidixic acid in rainbow trout (Oncorhynchus mykiss).

1. The pharmacokinetics, disposition and bioavailability of nalidixic acid were examined in Rainbow Trout following i.v. and per os administration (5 mg/kg). 2. Nalidixic acid was biexponentially eliminated from plasma following i.v. dosing (t1/2 alpha = 0.06 h, t1/2 beta = 23.0 h). The volume of distribution (Vss) and total body clearance (Clb) were 964.7 ml/kg and 31.5 ml/kg/h, respectively. 3. In vitro plasma protein binding was specific and saturable over a range of concentrations from 0.43 microM to 20.0 mM. Binding was approx. 26% at kinetically relevant plasma concentrations. 4. Apparent oral bioavailability was determined to be > 100%, suggesting that nalidixic acid was largely bioavailable and non-linear pharmacokinetics were evoked. 5. Oral studies demonstrated the highest 14C nalidixic acid equivalent concentrations in bile, intestine and liver. Muscle contained intermediate concentrations but among all organs accounted for the greatest total amount of drug (12.2% of dose). Mass balance studies demonstrated composite values for per cent of dose administered of 23.7, 18.8, 8.5, 10.0, 7.4 and 2.3% for 1, 2, 3, 6, 9 and 15 days, respectively. 6. A glucuronic acid conjugate of nalidixic acid was identified by n.m.r. and mass spectral analysis as the single primary metabolite.

Comparative pharmacokinetics and bioavailability of oxolinic acid and oxytetracycline in rainbow trout (Oncorhynchus mykiss).

1. The pharmacokinetics and bioavailability of oxolinic acid and oxytetracycline were studied in rainbow trout at a water temperature of 16 degrees C after intravascular (10 and 20 mg/kg, respectively) and oral (75 mg/kg) dosing. 2. The pharmacokinetics were best described by a two-compartment open model giving distribution half-lives of 0.31 h and 1.53 h, and elimination half-lives of 69.7 h and 60.3 h for oxolinic acid and oxytetracycline, respectively. The respective volumes of distribution (Vdarea) were 1.94 l/kg and 1.34 l/kg. 3. The apparent oral bioavailability for oxolinic acid and oxytetracycline was 13.6% and 5.6%. 4. The plasma protein binding was 27% for oxolinic acid and 55% for oxytetracycline. 5. Both drugs were well tolerated, the acute oral toxicities (LD50) exceeding 4000 mg/kg.

Reservoir of quinolone residues in fish.

Different tissues from salmon treated with the quinolones oxolinic acid, flumequine, enrofloxacin and sarafloxacin were analysed in search of possible reservoirs of the drugs. Residues of oxolinic acid and flumequine seem to be especially bound to bone, enrofloxacin to skin, and sarafloxacin to both skin and bone. The results showed that residues of these drugs were present in the fish for prolonged periods after the end of treatment.

Determination of oxolinic acid residues in salmon muscle tissue by liquid chromatography with fluorescence detection.

The present paper describes a method for determination of oxolinic acid in salmon muscle tissue. Tissue (0.5-2 g) mixed with 2 g anhydrous sodium sulfate is extracted twice with ethyl acetate, centrifuged, and the extract evaporated. The residue is partitioned in a mixture of hexane and 0.01M oxalic acid and the aqueous phase chromatographed using fluorescence detection at 327 nm excitation and 369 nm emission. Calibration and standard curves are linear from 10-200 ppb and 100-2000 ppb at different sensitivity settings. Recoveries ranged from 71-83% in spiked blanks, with a CV of 4-10.3% over a 2-week period. Preliminary results in treated salmon were variable, possibly because some fish refused to eat medicated feed.

Oxolinic acid in the trout: bioavailability and tissue residues.

A study was performed on the serum bioavailability and tissue elimination of oxolinic acid in the trout. The compound was added to the diet and administered at a dosage-level of 12 mg/kg/day for 7 consecutive days. The study utilized an analytical technique, high performance liquid chromatography, which has been described in detail here. The results obtained demonstrate that serum concentrations higher than the MIC for the control of the target pathogens (Aeromonas and Yersinia) can by sustained throughout the treatment period. The same positive results were observed in the tissues. Besides, on the base of a tolerance level of 0.05 ppm for the residue levels of oxolinic acid in the edible tissues (muscle mass and skin), a withdrawal time of six days after interruption of the prescribed treatment can be proposed.