Active Metabolite Ciprofloxacin Research Articles

Population pharmacokinetic analysis of enrofloxacin and its active metabolite ciprofloxacin after intravenous injection to cats with reduced kidney function.

It is unknown if enrofloxacin accumulates in plasma of cats with reduced kidney function. To determine if enrofloxacin and its active metabolite ciprofloxacin have reduced clearance in azotemic cats. Thirty-four cats hospitalized for clinical illness with variable degree of kidney function. Prospective study. After enrofloxacin (dose 5 mg/kg) administration to cats, sparse blood sampling was used to obtain 2 compartment population pharmacokinetic results using nonlinear mixed-effects modeling. Plasma enrofloxacin and ciprofloxacin concentrations were measured and summed to obtain the total fluoroquinolone concentration. A model of ciprofloxacin metabolism from enrofloxacin was created and evaluated for covariate effects on clearance, volume of distribution, and the metabolic rate of ciprofloxacin generation from enrofloxacin. Body weight was the only covariate found to affect total fluoroquinolone volume of distribution (effect 1.63, SE 0.19, P < .01) and clearance (effect 1.63, SE 0.27, P < .01). Kidney function did not have a significant effect on total fluoroquinolone clearance (median 440.8 mL/kg/h (range 191.4-538.0 mL/kg/h) in cats with normal kidney function, 365.8 mL/kg/h (range 89.49-1092.0 mL/kg/h) in cats with moderate kidney dysfunction, and 308.5 mL/kg/h (range 140.20-480.0 mL/kg/h) in cats with severe kidney dysfunction (P = .64). Blood urea nitrogen concentration influenced the metabolic generation of ciprofloxacin from enrofloxacin (effect 0.51, SE 0.08, P < .01), but other markers of kidney function did not. Adjustment of enrofloxacin dosage is not indicated for azotemic cats.

Plasma and muscle tissue disposition of enrofloxacin in Nile tilapia (Oreochromis niloticus) after intravascular, intraperitoneal, and oral administrations

The aim of the study was to investigate the plasma and muscle pharmacokinetic of enrofloxacin (ENR) and its active metabolite ciprofloxacin (CIP) in Nile tilapia (Oreochromis niloticus) following single intravascular (IV), intraperitoneal (IP), or oral (PO) administration at 30 ± 1 °C. In this study, 234 healthy Nile tilapia (120–150 g) were used. The fish received a single IV, IP, or PO treatment of ENR at a dose of 10 mg/kg. The plasma and muscle tissue concentrations of ENR and CIP were measured using high–performance liquid chromatography with fluorescence detection and were evaluated using non–compartmental analysis. The elimination half–life, volume of distribution at steady state, and total body clearance of ENR were 21.7 h, 2.69 L/kg, and 0.09 L/h/kg, respectively. The peak plasma concentrations of ENR after IP or PO administration were 6.11 and 4.21 µg/mL at 0.25 and 2 h, respectively. The bioavailability of ENR for IP or PO routes was 78% and 86%, respectively. AUC(0–120)muscle/AUC(0–120)plasma ratios following the IV, IP, or PO administrations were 1.43, 1.49, and 1.07, respectively. CIP was detected after all routes, but the AUC0–last ratios of CIP to ENR were <1.0% for plasma and muscle. ENR was detected up to 120 h following the IV, IP, or PO administrations. The long residence time of ENR after single IV, IP, or PO administration ensured the plasma concentration was ≥1 × MIC for bacteria with threshold MIC values of 0.92, 0.72, and 0.80 μg/mL over the whole 120 h observed. However, further studies are necessary to determine the optimum pharmacokinetic/pharmacodynamics data of ENR for the treatment of infections caused by susceptible bacteria in tilapia.

Culturing of primary bovine mammary epithelial cells and validation of biotransformation capacity in experiments with enrofloxacin

Many drugs and toxic compounds are subjected to disposition and metabolism in bovine mammary epithelial cells (bMECs). For rapid investigation of different compounds and their possible interactions, validated in vitro models are needed. Therefore, the first objective of described experiments was to develop the techniques for cell isolation, purification and culturing of bMECs. The second objective was the application of these cell cultures in a well-known substrate for one of the major biotransformation enzymes in epithelial cells. To this end, the metabolism of enrofloxacin (ENR) into its active metabolite ciprofloxacin (CPR), was studied. This conversion is known to be catalysed by enzymes of the cytochrome P4501A and P4503A family. The expression profile of these enzymes shows a close correlation with cellular ABC-efflux transporters. Primary bMECs were isolated from healthy udders of lactating cows (n=5 animals). mRNA levels of α-casein, b-lactoferrin and cyclophilin B were determined as markers of cell identity of purity of the cultures. Subsequently, bMECs cultures were incubated with ENR (10 µM). Concentrations of ENR and its main metabolite CPR in the medium and in the cells were determined by HPLC-FL analysis. Gene expression of CYP1A1, CYP1A2 and CYP3A4, bovine ABCG2 was detected by qRT-PCR. Results showed that ENR penetrated into bMECs and was converted to CPR. CPR was excreted in the medium suggesting participation of ABCG2 in fluoroquinolone efflux. In conclusion, the data showed that the established bMEC cultures expressed major CYP450 enzymes as well as the most relevant efflux transport ABGG2. This model should be further validated and can serve as an interesting model for further studies on site-specific drug/toxin metabolism and transport in the bovine mammary gland.

Fluoroquinolone exposure in utero did not affect articular cartilage of resulting foals.

Recent studies have shown that fluoroquinolones, specifically, enrofloxacin and its active metabolite (ciprofloxacin), cross the equine placenta without causing gross or histological lesions in the first and third trimester fetuses or resulting foal. However, it is possible that in utero exposure to fluoroquinolones may cause subtle lesions not detectable by standard means; thus, a more in-depth assessment of potential toxicity is warranted. To use quantitative magnetic resonance imaging (qMRI), biomechanical testing, and chondrocyte gene expression to evaluate the limbs of foals exposed to enrofloxacin during the third trimester of pregnancy. In vivo and control terminal experiment. Healthy mares at 280days gestation were assigned into three groups: untreated (n=5), recommended therapeutic (7.5mg/kg enrofloxacin, PO, SID, n=6) or supratherapeutic (15mg/kg, PO, SID, n=6) doses for 14days. Mares carried and delivered to term and nursed their foals for ~30days. Two additional healthy foals born from untreated mares were treated post-natally with enrofloxacin (10mg/kg PO, SID, for 5days). By 30days, foal stifles, hocks, elbows, and shoulders were radiographed, foals were subjected to euthanasia, and foal limbs were analysed by quantitative MRI, structural MRI, biomechanical testing and chondrocyte gene expression. Osteochondral lesions were detected with both radiography and structural MRI in foals from both enrofloxacin-treated and untreated mares. Severe cartilage erosions, synovitis and joint capsular thickening were identified in foals treated with enrofloxacin post-natally. Median cartilage T2 relaxation times differed between joints but did not differ between treatment groups. A small sample size was assessed and there was no long-term follow-up. While further research is needed to address long-term foal outcomes, no differences were seen in advanced imaging, biomechanical testing or gene expression by 30days of age, suggesting that enrofloxacin may be a safe and useful antibiotic for select bacterial infections in pregnant mares.

Pharmacokinetic profile of enrofloxacin and its metabolite ciprofloxacin in Asian house geckos (Hemidactylus frenatus) after single-dose oral administration of enrofloxacin

The pharmacokinetics of enrofloxacin and its active metabolite ciprofloxacin were determined following oral administration in 21 Asian house geckos (Hemidactylus frenatus) at a dose of 10 mg/kg. Changes in enrofloxacin and ciprofloxacin plasma concentrations were quantified at regular intervals over 72 h (1, 2, 6, 12, 24, 48, and 72 h). Samples were analysed by high-pressure liquid chromatography (HPLC) and the enrofloxacin pharmacokinetic data underwent a two-compartment analysis. Due to the limited ciprofloxacin plasma concentrations above the lower limit of quantification (LLOQ), the ciprofloxacin data underwent non-compartment analysis and the half-life was determined by the Lineweaver-Burke plot and analysis. The enrofloxacin and ciprofloxacin mean half-lives (t½) were 0.95 h (α) / 24.36 h (β), and 11.06 h respectively, area under the curve (AUC0-24h) were 60.56 and 3.14 µg/mL*h, respectively, maximum concentrations (Cmax) were 12.31 and 0.24 µg/mL, respectively, and time required to reach the Cmax (Tmax) were 1 and 2 h respectively. Enrofloxacin was minimally converted to the active metabolite ciprofloxacin, with ciprofloxacin concentrations contributing only 4.91% of the total fluoroquinolone concentrations (AUC0-24h). Based on the pharmacokinetic indices when using susceptibility breakpoints when determined at mammalian body temperature it is predicted that single oral administration of enrofloxacin (10 mg/kg) would result in plasma concentrations effective against susceptible bacterial species inhibited by an enrofloxacin MIC ≤ 0.5 µg/mL in vitro, but additional studies will be required to determine its efficacy in vivo.

Persistence and availability of veterinary antibiotics in soil and soil-manure systems

The availability and persistence of various antibiotics in soil and soil amended with composted poultry manure were investigated through laboratory incubation assays. Six veterinary antibiotics (one fluoroquinolone, two tetracyclines, two sulfonamides and one lincosamide) and one active metabolite (ciprofloxacin) were studied. The incubation assays were conducted at a controlled temperature of 25 °C with different water regimes, such as constant moisture content (80% of water holding capacity) and drying-rewetting cycles. The studied antibiotics were determined in soil and soil aqueous phase samples by LC-MS/MS using internal standards. The results indicated that the highest levels found in the soil aqueous phase were for sulfamethoxazole, followed by sulfamethazine and lincomycin, being very low the levels of chlortetracycline, doxycycline, ciprofloxacin and enrofloxacin (≤1.8%). A positive correlation was observed between the antibiotic concentrations and the content of the dissolved organic carbon in soil aqueous phase with the incubation time. An increase in the apparent sorption coefficients of these antibiotics, except chlortetracycline and lincomycin, was observed when the soil was amended with composted manure. Except for fluoroquinolones, with remaining residues around 70% after 90 days of incubation, a fast dissipation of antibiotics was observed during the assay, with half-lives ranging from 8 to 27 days. These values increased between 6% and 53% in manure amended soil; nevertheless, half-lives remained short (9 days and 27 days for lincomycin and sulfamethazine, respectively). Similar results were obtained with soil under drying-rewetting cycles showing somewhat lower values in soil aqueous phase and slightly shorter half-lives in some cases. The results obtained pointed out that the route of entry of antibiotics into the soil, through recycled water or manure, may have an important effect on their behavior, particularly regarding their availability in soil.

Enrofloxacin and Its Active Metabolite Ciprofloxacin Cross the Equine Placenta and Did not Cause Lesions in the Articular Surface of the Fetuses and Foals

Increased ambient temperatures has been identified to contribute to reproductive outcomes for several domesticated species, but its impact on equine reproduction has not been previously investigated. Therefore, this study aimed to examine the relationship between ambient climatic conditions, as measured by temperature-humidity index (THI) between day 7 and day 14 of gestation, and early embryonic loss (EEL) in recipient mares undergoing embryo transfer.The study examined records from 834 embryo transfers at an equine breeding facility in Victoria, Australia. Early embryonic loss was defined as a negative transrectal ultrasound on day 14 of gestation after an embryo was transferred on day 7. Both maximum THI on the day of transfer (day 7) and mean THI between day 7 and day 14 were investigated for association with the outcome of EEL using multivariable logistic regression, controlling for confounders including embryo age and quality, recipient mare quality and embryo transfer quality.EEL was observed in 21% of embryo transfers. A five-unit increase in maximum THI on the day of transfer was associated with an 18% increase in the odds of EEL (p = 0.01). Similarly, the odds of EEL increased by 25% for each five-unit increase in mean THI between day 7 and 14 (p = 0.003).As both single and cumulative episodes of high THI were associated with increased EEL in embryo transfer mares from this equine breeding facility, further studies are warranted to identify similar effects in a broader population, establish causality and evaluate possible mitigation strategies in anticipation of heat waves.

Pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin following single-dose subcutaneous injection in black-tailed prairie dogs (Cynomys ludovicianus).

OBJECTIVE To determine plasma concentrations of enrofloxacin and its active metabolite ciprofloxacin following single-dose SC administration to black-tailed prairie dogs (Cynomys ludovicianus). ANIMALS 8 captive healthy 6-month-old sexually intact male black-tailed prairie dogs. PROCEDURES Enrofloxacin (20 mg/kg) was administered SC once to 6 prairie dogs and IV once to 2 prairie dogs. A blood sample was collected from each animal immediately before (0 hours) and 0.5, 1, 2, 4, 8, 12, and 24 hours after drug administration to evaluate the pharmacokinetics of enrofloxacin and ciprofloxacin. Plasma enrofloxacin and ciprofloxacin concentrations were quantified with ultraperformance liquid chromatography-mass spectrometry, and noncompartmental pharmacokinetic analysis was performed. RESULTS Enrofloxacin was biotransformed to ciprofloxacin in the prairie dogs used in the study. For total fluoroquinolones (enrofloxacin and ciprofloxacin), the mean (range) of peak plasma concentration, time to maximum plasma concentration, and terminal half-life after SC administration were 4.90 μg/mL (3.44 to 6.08 μg/mL), 1.59 hours (0.5 to 2.00 hours), and 4.63 hours (4.02 to 5.20 hours), respectively. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that administration of enrofloxacin (20 mg/kg, SC, q 24 h) in black-tailed prairie dogs may be appropriate for treatment of infections with bacteria for which the minimum inhibitory concentration of enrofloxacin is ≤ 0.5 μg/mL. However, clinical studies are needed to determine efficacy of such enrofloxacin treatment.

Effect of bovine ABCG2 Y581S polymorphism on concentrations in milk of enrofloxacin and its active metabolite ciprofloxacin

The ATP-binding cassette transporter G2 (ABCG2) is involved in the secretion of several drugs into milk. The bovine Y581S ABCG2 polymorphism increases the secretion into milk of the fluoroquinolone danofloxacin in Holstein cows. Danofloxacin and enrofloxacin are the fluoroquinolones most widely used in veterinary medicine. Both enrofloxacin (ENRO) and its active metabolite ciprofloxacin (CIPRO) reach milk at relatively high concentrations. The aim of this work was to study the effect of the bovine Y581S ABCG2 polymorphism on in vitro transport as well as on concentrations in plasma and in milk of ENRO and CIPRO. Experiments using cells overexpressing bovine ABCG2 showed the effects of ABCG2 on the transport of CIPRO, demonstrating more efficient in vitro transport of this antimicrobial by the S581 variant as compared with the Y581 variant. Animal studies administering 2.5mg/kg of ENRO subcutaneously to Y/Y 581 and Y/S 581 cows revealed that concentrations in plasma of ENRO and CIPRO were significantly lower in Y/S animals. Regardless of the genotype, the antimicrobial profile in milk after the administration of ENRO was predominantly of CIPRO. With respect to the genotype effects on the amounts of drugs present in milk, AUC0–24 values were more than 1.2 times higher in Y/S cows for ENRO and 2.2 times for CIPRO, indicating a greater capacity of Y581S to transfer these drugs into milk. These results emphasize the clinical relevance of this polymorphism as a factor affecting the concentrations in plasma and in milk of drugs of importance in veterinary medicine.

POPULATION PHARMACOKINETICS OF ENROFLOXACIN AND ITS METABOLITE CIPROFLOXACIN IN THE GREEN SEA URCHIN (STRONGYLOCENTROTUS DROEBACHIENSIS) FOLLOWING INTRACOELOMIC AND IMMERSION ADMINISTRATION.

Sea urchin mass mortality events have been attributed to both infectious and noninfectious etiologies. Bacteria, including Vibrio spp. and Pseudoalteromonas spp., have been isolated during specific mortality events. Aquarium collection sea urchins are also subject to bacterial infections and could benefit from antimicrobial treatment, but pharmacokinetic studies have been lacking for this invertebrate group until recently. This study evaluated the pharmacokinetics of enrofloxacin and its active metabolite ciprofloxacin in the green sea urchin (Strongylocentrotus droebachiensis) after intracoelomic injection and medicated bath immersion administration. The utility of a population pharmacokinetic method using nonlinear mixed effects modeling (NLME) was also evaluated. Thirty sea urchins were assigned to either the injection or immersion group. Twelve study animals and three untreated controls were utilized for each administration method: enrofloxacin 10 mg/kg intracoelomic injection or a 6-hr enrofloxacin 10 mg/L immersion. Each animal was sampled four times from 0 to 120 hr. Water samples were collected during immersion treatment and posttreatment time points in both groups. Hemolymph and water sample drug concentrations were analyzed using high-performance liquid chromatography, and pharmacokinetic parameters were determined using an NLME population pharmacokinetic method. Enrofloxacin concentrations were fit to a two-compartment model with first-order input for the intracoelomic injection group. The enrofloxacin elimination half-life (t½), peak hemolymph concentration (CMAX), and area under the curve (AUC) were 38.82 hr, 90.92 μg/ml, and 1,199 hr·μg/ml, respectively. Enrofloxacin was modeled to a one-compartment model with first-order input for the immersion treatment. The enrofloxacin t½, CMAX, and AUC were 33.46 hr, 0.48 μg/ml, and 32.88 hr·μg/ml, respectively. Ciprofloxacin was detected in trace concentrations in all hemolymph samples, indicating minimal production of this metabolite. The concentrations of enrofloxacin achieved far exceeded minimum inhibitory concentrations reported for teleost pathogens. No adverse effects were associated with enrofloxacin administration by either treatment method or from hemolymph sampling.

Pharmacokinetics of Enrofloxacin in Emu (Dromaius novaehollandiae) Birds After Intravenous and Oral Bolus Administration

Pharmacokinetics of enrofloxacin was studied after intravenous and oral bolus administration at 10 mg/kg in healthy emus aged between 18 and 24 months. Blood samples were collected from jugular vein at predetermined time intervals after drug administration. Enrofloxacin and its active metabolite ciprofloxacin in plasma were determined by HPLC. Plasma concentrations versus time were analyzed by a non-compartmental analysis. For i.v. and oral bolus dose of administration, elimination half-life (t1/2β) was 4.364 ± 0.179 and 4.125 ± 0.361 h, respectively; AUC0–∞ was 20.085 ± 3.493 and 16.056 ± 1.436 µg h/mL, respectively; mean residence time (MRT) was 5.105 ± 0.216 and 6.616 ± 0.475 h, respectively; volume of distribution was 3.921 ± 1.005 and 3.171 ± 0.296 L/kg, respectively and total body clearance was 0.629 ± 0.164 and 0.507 ± 0.003 L/h kg, respectively. Mean absolute bioavailability for enrofloxacin after oral administration was 79.941 ± 7.147 %. The metabolite ciprofloxacin could be detected from 15 min to 24 h following i.v. and oral administration of enrofloxacin. The ratio of AUC0–tcipro/AUC0–tenro was 7.764 and 9.031 %, respectively for i.v. and oral administration of enrofloxacin. The t1/2β and MRT of the metabolite were longer than those of parent substance. From the PK/PD indices such as Cmax/MIC, AUC/MIC and Cmax/MPC, AUC/MPC study, the recommended doses of enrofloxacin in emu birds were 10 mg/kg body weight once daily for i.v. and oral routes against organisms susceptible to 0.25 and 0.125 μg/mL, respectively. Taking the PAE and active metabolite ciprofloxacin into consideration, it is recommended that enrofloxacin could be used at the dose rate of 10 mg/kg at every 24 h even against the organisms susceptible to 0.5 µg/mL.

Comparison of plasma and tissue disposition of enrofloxacin in rainbow trout (Oncorhynchus mykiss) and common carp (Cyprinus carpio) after a single oral administration

The aim of the study was to investigate the serum and tissue disposition of enrofloxacin and its active metabolite ciprofloxacin in rainbow trout (Oncorhynchus mykiss) and common carp (Cyprinus carpio) after a single oral administration at a dose of 10 mg kg–1. Concentrations of enrofloxacin in the serum of rainbow trout showed high variability with two peaks at the third and 24th hour after administration. The highest concentrations were found in the liver. The curves of liver levels showed similar changes to the respective serum samples. In the muscles, enrofloxacin concentrations were also higher compared with the respective serum samples. Ciprofloxacin concentrations were lower and showed smaller variations in all investigated tissues. The serum and tissue concentrations of enrofloxacin and ciprofloxacin in common carp showed two peaks, with the first Cmax at the third hour after drug administration as in rainbow trout. Concentrations of both investigated substances were higher in the liver than in the serum. The differences in common carp were less pronounced in comparison with rainbow trout. Relatively high levels of both substances were found in the muscles. Seven days after treatment enrofloxacin concentrations in the serum and tissues were within the therapeutic levels for most of the sensitive microorganisms in trout. Lower concentrations of its metabolite ciprofloxacin were found in the investigated tissues at the last sampling point. Lower levels of both substances were found in carp.

Tissue Concentrations of Enrofloxacin and Its Metabolite Ciprofloxacin after a Single Topical Dose in the Coqui Frog (Eleutherodactylus coqui)

Tissue concentrations of the fluoroquinolone antimicrobial enrofloxacin and its active metabolite ciprofloxacin were determined over a 24 h period after a single topical application in the coqui frog (Eleutherodactylus coqui). Twelve frogs, scheduled for euthanasia unrelated to the study (due to exposure to a potentially lethal ranavirus), were randomly divided into four groups of three animals. Three groups received one dose of enrofloxacin topically (10 mg/kg), and the remaining group served as an untreated control. One group was euthanized and tissues (liver, kidneys) were collected at each of the following time points: 0 (control), 6, 12, and 24 h posttreatment. Tissues were pooled within each group, and concentrations of enrofloxacin and ciprofloxacin were measured using high-pressure liquid chromatography. Enrofloxacin tissue concentrations ranged from 0.2 to 0.44 μg/g, whereas ciprofloxacin concentrations ranged from 0.42 to 0.81 μg/g. Wildlife Conservation Society amphibian microbiology records from 2000 to 2010 were reviewed, and bacterial isolates and minimum inhibitory concentrations were determined. This study demonstrates that enrofloxacin is absorbed systemically after topical administration to coqui frogs, converts to ciprofloxacin, and results in measurable tissue concentrations for at least 24 h.

Distribution of enrofloxacin and its active metabolite, using anin vivoultrafiltration sampling technique after the injection of enrofloxacin to pigs

The objective of this study was to determine the pharmacokinetics (PK) of enrofloxacin in pigs and compare to the tissue interstitial fluid (ISF). Six healthy, young pigs were administered 7.5 mg/kg enrofloxacin subcutaneously (SC). Blood and ISF samples were collected from preplaced intravenous catheters and ultrafiltration sampling probes placed in three different tissue sites (intramuscular, subcutaneous, and intrapleural). Enrofloxacin concentrations were measured using high-pressure liquid chromatography with fluorescence detection, PK parameters were analyzed using a one-compartment model, and protein binding was determined using a microcentrifugation system. Concentrations of the active metabolite ciprofloxacin were negligible. The mean ± SD enrofloxacin plasma half-life, volume of distribution, clearance, and peak concentration were 26.6 ± 6.2 h (harmonic mean), 6.4 ± 1.2 L/kg, 0.18 ± 0.08 L/kg/h, and 1.1 ± 0.3 μg/mL, respectively. The half-life of enrofloxacin from the tissues was 23.6 h, and the maximum concentration was 1.26 μg/mL. Tissue penetration, as measured by a ratio of area-under-the-curve (AUC), was 139% (± 69%). Plasma protein binding was 31.1% and 37.13% for high and low concentrations, respectively. This study demonstrated that the concentration of biologically active enrofloxacin in tissues exceeds the concentration predicted by the unbound fraction of enrofloxacin in pig plasma. At a dose of 7.5 mg/kg SC, the high tissue concentrations and long half-life produce an AUC/MIC ratio sufficient for the pathogens that cause respiratory infections in pigs.

In vitro killing of Escherichia coli, Staphylococcus pseudintermedius and Pseudomonas aeruginosa by enrofloxacin in combination with its active metabolite ciprofloxacin using clinically relevant drug concentrations in the dog and cat

Enrofloxacin is a fluoroquinolone antibacterial agent used to treat infections in companion animals. Enrofloxacin's antimicrobial spectrum includes Gram positive and Gram-negative bacteria and demonstrates concentration-dependent bacteriocidal activity. In dogs and cats, enrofloxacin is partially metabolized to ciprofloxacin and both active agents circulate simultaneously in treated animals at ratios of approximately 60–70% enrofloxacin to 30–40% ciprofloxacin. We were interested in determining the killing of companion animal isolates of Escherichia coli, Staphylococcus pseudintermedius and Pseudomonas aeruginosa by enrofloxacin and ciprofloxacin combined using clinically relevant drug concentrations and ratios. For E. coli isolates exposed to 2.1 and 4.1μg/ml of enrofloxacin/ciprofloxacin at 50:50, 60:40 and 70:30 ratios, a 1.7–2.5log10 reduction (94–99% kill) was seen following 20min of drug exposure; 0.89–1.7log10 (92–99% kill) of S. pseudintermedius following 180min of drug exposure; 0.85–3.4log10 (98–99% kill) of P. aeruginosa following 15min of drug exposure. Killing of S. pseudintermedius was enhanced in the presence of enrofloxacin whereas killing of P. aeruginosa was enhanced in the presence of ciprofloxacin. Antagonism was not seen when enrofloxacin and ciprofloxacin were used in kill assays. The unique feature of partial metabolism of enrofloxacin to ciprofloxacin expands the spectrum of enhanced killing of common companion animal pathogens.

ENROFLOXACIN-IMPRINTED MONOLITHIC HPLC COLUMNS SYNTHESIZED BY IN SITU COPOLYMERIZATION FOR CHROMATOGRAPHIC SEPARATION

A monolithic molecularly imprinted polymer for enrofloxacin was synthesized by in situ copolymerization of methylacrylic acid and methyl methacrylate in a traditional stainless-steel chromatographic column for the rapid separation and determination of enrofloxacin and ciprofloxacin in eggs. By optimizing the polymerization condition, the monolithic MIP showed highly specific recognition for enrofloxacin over its active metabolite ciprofloxacin. The influence of components of monomers on hydrophobicity, contractibility, selectivity, and binding capacity of polymer were investigated. As shown by SEM, the mesopores and macropores were formed in the monolith column; this allowed the mobile phase to flow through the column with low backpressure. Furthermore, some chromatographic conditions such as mobile phase composition and flow rate on the retention times were investigated. The binding capacity was evaluated by static adsorption and Scatchard analysis, which showed that the dissociation constant and the maximum binding capacity were 117.7 mg/L and 27.27 mg/g for high affinity binding site, and 297 mg/L and 187.4 mg/g for lower affinity binding site, respectively. The mean recoveries of enrofloxacin and ciprofloxacin from egg samples were 103.3–115% and 89.3–95.1%, respectively. The research has shown that copolymerization provides more adjustable conditions for making molecularly imprinted monolithic columns with different morphologies and higher selectivity.

Pharmacokinetics of enrofloxacin after single intravenous administration in sheep

The disposition of enrofloxacin in sheep was investigated after single-dose intravenous administration of 2.5 mg/kg body weight. Blood samples were drawn from the jugular vein at predetermined times after drug administration. Plasma concentrations of enrofloxacin and its active metabolite ciprofloxacin were simultaneously determined by reverse-phase high performance liquid chromatography. The data collected were subjected to non-compartmental and compartmental kinetic analysis. Statistical model theory was used to determine non-compartmental pharmacokinetic parameters. Disposition of enrofloxacin was described by a three-compartment open model with elimination from the central compartment following intravascular administration. The elimination half-life, the volume of distribution, and the area under the concentration vs time curve (AUC) were 4.31 h, 1.10 l/kg and 9.24 microg x h/ml, respectively. Enrofloxacin was metabolised to ciprofloxacin and the ratio between the AUCs of ciprofloxacin and enrofloxacin was 0.26 after intravenous administration. With predictive models of efficacy (maximum plasma concentrations/minimum inhibitory concentrations [Cmax/MIC] and AUC/MIC ratios in plasma) for most of the sheep pathogen microorganisms, enrofloxacin produced scores higher than 15 and 50, respectively. After intravenous administration atthe dose of 2.5 mg/kg, enrofloxacin achieved concentrations several times above the MIC for major pathogen bacteria in plasma, and it may prove useful in the treatment of infectious diseases caused by sensitive pathogens in sheep.

Penetration of enrofloxacin into the nasal secretions and relationship between nasal secretions and plasma enrofloxacin concentrations after intramuscular administration in healthy pigs

The pharmacokinetic behaviour of enrofloxacin (ENRO) in plasma and nasal secretions of healthy pigs was investigated, after a single-dose intramuscular administration of 2.5 mg/kg body weight of the drug. Blood samples and nasal secretions were collected at predetermined times after drug administration. Concentrations of ENRO and its active metabolite ciprofloxacin (CIPRO) were determined in plasma and nasal secretions by high-performance liquid chromatography (HPLC). CIPRO was not detected probably because we investigated young weaned pigs. The data collected in 12 pigs for ENRO were subjected to noncompartmental analysis. In plasma, the maximum concentration of drug (C(max)), the time at which this maximum concentration of drug (T(max)) was reached, the elimination half-life (t(1/2)(beta)) and the area under the concentration vs. time curve (AUC) were, respectively, 694.7 ng/mL, 1.0 h, 9.3 h and 8903.2 ngxh/mL. In nasal secretions, C(max), T(max), t(1/2)(beta) and AUC were, respectively, 871.4 ng/mL, 2.0 h, 12.5 h and 11 198.5 ngxh/mL. In a second experiment conducted in 10 piglets, the relationship between concentrations of ENRO measured in the plasma and the nasal secretions has been determined following single-dose intramuscular administration of 2.5, 10 or 20 mg/kg body weight of the drug. It has been demonstrated that, among several variables, i.e., (1) the dose administered, (2) the time between intramuscular injection and blood sampling, (3) the age, (4) the sex, (5) the animal body weight and (6) the plasma concentration of the drug, only the latter influenced significantly the ENRO concentration in nasal secretions. Practically, using a generalized linear mixed model, ENRO concentrations in the nasal secretions (microg/mL) can be predicted taking into account the ENRO concentrations in plasma (microg/mL), according to the following equation:

Molecularly Imprinted Monolithic Column for Selective On-Line Extraction of Enrofloxacin and Ciprofloxacin from Urine

A simple on-line molecularly imprinted solid-phase extraction coupled with liquid chromatographic separation was developed for the simultaneous determination of enrofloxacin and its active metabolite ciprofloxacin from urine samples. The molecularly imprinted monolithic columns were synthesized in water-containing systems using norflorxacin as dummy template and methanol–water (5:1, v/v) as porogenic solvent, which reveal high affinity to enrofloxacin and ciprofloxacin in the aqueous environment. Due to the unique porous structure and flow-through channels existing in the network skeleton of the imprinted monolith, urine samples could be injected directly into the imprinted column, proteins and other biological matrix were quickly washed out and the analytes were selectively retained and enriched. Good linearity was obtained from 0.05 to 200 mg L−1 with relative standard deviations less than 3.1%. The recoveries were higher than 87% at three different concentrations and the limit of detection of the method was 0.01 mg L−1. Moreover, by increasing the injection volume, the sensitivity of the method could be further improved.

A pharmacokinetic study of enrofloxacin and its active metabolite ciprofloxacin after oral and intramuscular dosing of enrofloxacin in rhesus monkeys (Macaca mulatta)

Enrofloxacin is used for treating Shigellosis in non-human primates; however, there are no reports describing its pharmacokinetics in rhesus monkeys. Pharmacokinetic data in intended target species (rhesus) help to determine the proper dose regimen. Blood levels of enrofloxacin and ciprofloxacin (enrofloxacin's active metabolite), were determined after either intramuscular or oral dosing of enrofloxacin for 7 days in a cross-over study. Levels of both antibiotics were determined by solid phase extraction followed by reversed-phase chromatography with tandem mass spectrometry. Results indicate enrofloxacin half-life after intramuscular dosing is estimated to be 2.4 hours. Enrofloxacin given either intramuscular or p.o. rapidly achieves satisfactory therapeutic blood levels of enrofloxacin or ciprofloxacin in rhesus monkeys. Results from these pharmacokinetic study parallel values published for other animal species. Our results show use of enrofloxacin is effective in managing Shigella infections in rhesus monkeys based upon achieving these blood drug levels.