In silico, in vitro and in vivo metabolite identification of brexpiprazole using ultra-high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry

RATIONALE

Brexpiprazole is a novel serotonin-dopamine activity modulator approved by the USFDA in July 2015 for the treatment of schizophrenia and as an adjunctive therapy with other antidepressants for major depressive disorder in adults. However, limited numbers of metabolites are reported in the literature for brexpiprazole. Our prime intent behind this study is to revisit metabolite profiling of brexpiprazole and to identify and characterize all possible in vitro and in vivo metabolites.

METHODS

Firstly, the site of metabolism for brexpiprazole was predicted by a Xenosite web predictor model. Secondly, in vitro metabolite profiling was performed by incubating the drug individually with rat liver microsomes, human liver microsomes and rat S9 fraction at 37°C for 1 h in incubator shaker. Finally, for in vivo metabolite identification, a 50 mg kg^-1 dose of brexpiprazole was administered to male Sprague-Dawley rats and the presence of various metabolites was confirmed in rat plasma, urine and feces.

RESULTS

The predicted atomic site of metabolism was obtained as a color gradient by the Xenosite web predictor tool and, from this study, probable metabolites were listed. In total, 14 phase I and 2 phase II metabolites were identified and characterized in the in vitro and in vivo matrices using ultra-high-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (UHPLC/QTOF-MS/MS). The majority of metabolites were found in the sample incubated with human liver microsomes and in rat urine, while in the other matrices only a few metabolites were detected.

CONCLUSIONS

All the 16 metabolites were identified and characterized using UHPLC/QTOF-MS/MS. The study revealed that brexpiprazole is metabolized via hydroxylation, glucuronidation, S-oxidation, N-oxidation, dioxidation, oxidative deamination, N-dealkylation, etc.

[Clinical and biochemical aspects of pathogenesis of urolithiasis]

AIM

To investigate the role of infection in the pathogenesis of urolithiasis using chromatography mass spectrometry analysis.

MATERIALS AND METHODS

The study analyzed clinical and laboratory data of 316 urolithiasis patients hospitalized between February 2005 and January 2015. All patients underwent a comprehensive clinical examination, including laboratory tests (hematological and biochemical blood tests, clinical and bacteriological tests of urine) and chromatography mass spectrometry analysis urine and blood. The laboratory testing was carried out both during the patients hospital stay and outpatient follow-up.

RESULTS

We analyzed the biological material for the presence of characteristic ions. Urine samples of 316 urolithiasis patients were found to contain activators of "cooperative sensitivity." Moreover, there was a significant increase in the concentration of signaling compounds of the "cooperative sensitivity" of microorganisms in patients with complicated urolithiasis in comparison with the control indices (lactones-0.006 plus/minus 0.0004 mmol/L, normal values less than 0.002, quinolones 0.004 plus/minus 0.0003 mmol/l, normal values - less than 0.002 and furan esters - 0.005 plus/minus 0.0004, normal values less than 0.002). Threshold values of the activators of "cooperative sensitivity" demonstrated the readiness of the microbial community to initiate an inflammatory process. The presence of activators such as lactones, quinolones and furan esters in the samples of urolithiasis patients predisposes to the activation of pathogenic genes in a large group of microorganisms, including gram positive and gram negative species.

DISCUSSION

In our opinion, to improve the quality of diagnostic, treatment and preventive measures in patients with different types of stone formation, it is advisable to use chromatography mass spectrometry analysis, which allows determination of priority clinical and laboratory indicators.

CONCLUSION

The data on the role of infection in the pathogenesis of urolithiasis obtained by chromatographic methods suggest the possibility of using the indicators of the activators of the "cooperative sensitivity" of microbes in patients with various forms of urolithiasis to assess the disease severity.

A capillary zone electrophoretic method for simultaneous determination of seven drugs in pharmaceuticals and in human urine

A simple, sensitive, and novel method has been developed and validated for the separation and simultaneous quantitation of seven structurally different drugs-pipemidic acid and ofloxacin quinolone antibiotics, pseudoephedrine decongestant, piroxicam anti-inflammatory, thiamin, pyridoxine, and cobalamin-in a mixture by capillary zone electrophoresis. Factors affecting the separation were pH, concentration of buffer, and applied voltage. Separation was carried out in < 9 min with a 50 mM sodium tetraborate buffer, pH 10, and an applied voltage of 30 kV in an uncoated silica capillary tube. The carrier electrolyte gave baseline separation with good resolution, reproducibility, and accuracy. Calibration plots were linear over at least three orders of magnitude of analyte concentrations, and the lower LODs were within the range of 1-5 microg/mL. Detection was performed by UV absorbance at 230 nm. The method was validated for the analysis of drugs in pharmaceutical preparations and in urine samples with RSD of 0.5-2.4% and recovery of > 99%.

Separation of fifteen quinolones by high performance liquid chromatography: Application to pharmaceuticals and ofloxacin determination in urine

A simple chromatographic method is described for assaying 15 quinolones and fluoroquinolones (pipemidic acid, marbofloxacin, enoxacin, ofloxacin, norfloxacin, ciprofloxacin, danofloxacin, lomefloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid, nalidixic acid, flumequine and piromidic acid), in urine and pharmaceutical samples. The determination was achieved by LC using an RP C18 analytical column. A mobile phase composed of mixtures of methanol-ACN-10 mM citrate buffer at pH 3.5 and 10 mM citrate buffer at pH 4.5, delivered under an optimum gradient program, at a flow rate of 1.5 mL/min, allows to accomplish the chromatographic separation in 26 min. For detection, diode-array UV-Vis at 280 nm and fluorescence detection set at excitation wavelength/emission wavelength: 280/450, 280/ 495, 280/405 and 320/360 nm were used. Detection and quantification limits were between 0.3-18 and 0.8-61 ng/mL, respectively. The method was validated in terms of interday (n = 6) and intraday (n = 6) precision and accuracy. The procedure was successfully applied to the analysis of human and veterinary pharmaceuticals. Also, ofloxacin was determined in human urine samples belonging to a patient undergoing treatment with this active principle, among others.

Concerns in the development of an assay for determination of a highly conjugated adsorption-prone compound in human urine

Concerns in pre-analytical handling of urine samples are discussed using a new KDR kinase inhibitor, 3-[5-(4-methanesulfonyl-piperazin-1-ylmethyl)-1H-indol-2-yl]-1H-quinolin-2-one (compound A), as an example of a case where high light sensitivity and low analyte recovery (high affinity for container surface) were found. The absence of these problems in plasma samples may be a result of the plasma protein content. Low recovery of the analyte from urine can be remedied by either changing the container or by using additives, such as bovine serum albumin (BSA) or non-ionic surfactant Tween-20. In the case of compound A, changing containers (polypropylene versus glass vial) or addition of BSA did bring analyte recovery up to 80%. However, the addition of 0.2% Tween-20 into urine quality controls (QCs) gave more than 95% analyte recovery, indicating effective reduction of analyte loss to the surface of containers. The urine assay using mixed-mode SPE and LC-MS/MS was not affected significantly by introducing Tween-20 into the samples. The mean SPE extraction recovery was 68.4% and matrix suppression of ionization on MS was less than 8% at all analyte concentrations. The linear range of the calibration curve was 0.5-400 ng/mL on PE Sciex API 3000 LC-MS/MS system. The assay intraday accuracy and precision were 92.1-104.8% and <4.2% (%CV), respectively. Urine QC samples, containing 0.2% Tween-20, gave excellent recovery after three cycles of freeze and thaw. Since analyte loss to its urine container surface is not unique to compound A (M. Schwartz, W. Kline, B. Matuszewski, Anal. Chim. Acta 352 (1997) 299-307; A.L. Fisher, E. DePuy, T. Shih, R. Stearns, Y. Lee, K. Gottesdiener, S. Flattery, M. De Smet, B. Keymeulen, D.G. Musson, J. Pharm. Biomed. Anal. 26 (2001) 739-752), we suggest an evaluation of the potential problem in the early stages of urine assay development to ensure reliable quantitation of analytes. The addition of Tween-20 can serve as a useful analytical tool to other analytes with similar situations.

Electrochemical Adsorptive Behavior of Some Fluoroquinolones at Carbon Paste Electrode

Cyclic voltammetry and differential pulse voltammetry were used to explore the adsorption behavior of three antibacterial agents at a carbon paste electrode. The drugs were accumulated on a carbon paste electrode, and a well-defined oxidation peak was obtained in acetate buffer (pH 5.0). The adsorptive stripping response was evaluated as a function of some variables such as the scan rate, pH and accumulation time. A simple, precise, inexpensive and sensitive voltammetric method has been developed for the determination of the cited drugs (Lomefloxacin (LFX), Sparfloxacin hydrochloride (SFX), and Gatifloxacin (GFX)). A linear calibration was obtained from 2 x 10(-7) M to 4 x 10(-5) M for LFX, 2 x 10(-7) M to 6 x 10(-5) M for SFX, and GFX. The limits of detection (LOD) were 4.2 x 10(-7), 7 x 10(-7) and 6.6 x 10(-7) M, while the limits of quantification (LOQ) were 1.4 x 10(-6), 2.3 x 10(-6) and 2.2 x 10(-6) M for LFX, SFX, and GFX, respectively. The R. S. D. of five measurements at the 1 x 10(-6) M level were 0.4, 0.5 and 0.3 for LFX, SFX and GFX, respectively. The method was applied to the determination of LFX, SFX and GFX in dilute urine samples and dosage forms, and compared with the HPLC method.

Evaluation of the effect of cephalexin and enrofloxacin on clinical laboratory measurements of urine glucose in dogs

OBJECTIVE

To determine the effects of cephalexin and enrofloxacin on results of 4 commercially available urine glucose tests in dogs.

ANIMALS

6 healthy adult female dogs.

PROCEDURE

In a crossover design, cephalexin (22 and 44 mg/kg [10 and 20 mg/lb], p.o., q 8 h) or enrofloxacin (5 and 10 mg/kg [2.3 and 4.5 mg/lb], p.o., q 12 h) was administered to dogs for 1 day. Urine samples were tested for glucose at 0, 6, and 24 hours after drug administration. In vitro, dextrose was added to pooled glucose-negative canine urine samples containing either no antimicrobial or known concentrations of either antimicrobial; urine samples were then tested for glucose.

RESULTS

In vivo, false-positive results were obtained by use of a tablet test in the presence of both antimicrobials and by use of a strip test in the presence of cephalexin. In vitro, false-positive results were obtained with the tablet test at the highest urine concentration of cephalexin (2,400 microg/mL) and with a strip test at the highest concentration of enrofloxacin (600 microg/mL). Enrofloxacin in urine samples containing dextrose caused the urine glucose tests to underestimate urine glucose concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Cephalexin and enrofloxacin at dosages used in clinical practice may result in false-positive or false-negative urine glucose results, and care should be taken when using urine as a basis for identifying or monitoring diabetic animals.

Pharmacoknetic study of diclofenac and its interaction with enrofloxacin in buffalo calves

A comparative pharmacokinetic study of diclofenac (1 mg/kg, i.v.) when given alone or in combination with enrofloxacin (4 mg/kg, i.v.) in five buffalo calves was carried out by using HPLC. The study revealed that the plasma concentrations of diclofenac were significantly lower (p<0.05) in combined administration of diclofenac with enrofloxacin (0.042 to 3 h), whereas significantly higher (p<0.05) levels of plasma drug concentrations were observed in later period (8 to 24 h). In urine, significantly lower (p<0.05) drug concentrations of diclofenac were observed from 0.167 to 1.5 h, whereas significantly higher (p<0.01) urine drug concentrations were observed in later period (4 to 48 h) when diclofenac was given in combination with enrofloxacin as compared to when diclofenac was given alone. Various kinetic parameters like A, Cpo and beta were significantly lower (p<0.05) whereas t1/2 beta, AUMC, MRT and various volume of distribution (VdC, VdB, Vdarea and VdSS) were significantly higher in combined administration of diclofenac with enrofloxacin as compared to when diclofenac was given alone (p<0.05).

The effect of endotoxin and dexamethasone on enrofloxacin pharmacokinetic parameters in swine

The impact of Escherichia coli-derived lipopolysaccharide (LPS) on the pharmacokinetic parameters of enrofloxacin in swine was assessed to determine whether this model would substitute for a pleuropneumonia infection model for pharmacokinetic evaluation of drugs. All animals received a single i.v. dose of enrofloxacin (5 mg/kg). Half the animals also received dexamethasone (0.5 mg/kg) to determine the impact of inflammation on any changes in enrofloxacin pharmacokinetics, as most of the effects of LPS are due to elaboration of inflammatory mediators. Administration of LPS alone (2.0 microg/kg) was associated with a decrease in clearance of enrofloxacin. Volume of distribution at steady state was increased in the dexamethasone-treated animals. The terminal elimination half-life of enrofloxacin was significantly increased in the LPS group. Dexamethasone administration, either alone or in combination with LPS challenge, increased the volume of distribution both at steady state and during the elimination phase. Lipopolysaccharide challenge did not affect the volume of distribution. Lipopolysaccharide challenge did not affect urinary excretion of enrofloxacin but did increase the urinary excretion of its principal metabolite, ciprofloxacin. However, the increased excretion did not begin until 24 h after administration of enrofloxacin. Because these pharamcokinetic results are different from those obtained with the pleuropneumonia model using the bacteria Actinobacillus pleuropneumoniae, the results of this study demonstrate that LPS is not a generic substitute for infection for the pharmacokinetic evaluation of drugs.

Studies on the metabolic fate of M17055, a novel diuretic (6). Assessment for drug-drug interactions of M17055 in metabolism, distribution and excretion

1. The potential of M17055, a novel diuretic candidate, to affect the activities of human CYP enzymes, alter the plasma unbound fraction and compete with concomitant drugs in renal secretion as part of an assessment for drug-drug interactions in metabolism, distribution and excretion was investigated. 2. The effects of M17055 on the activities of human CYP1A2, CYP2E1, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 were considered negligible at clinically relevant concentrations. 3. The majority of M17055 (99%) was bound to human plasma proteins, but it is unlikely to alter the binding of other clinically relevant drugs. 4. The renal clearance of M17055 (corrected for the plasma unbound fraction in male rats) substantially exceeded the glomerular filtration rate and was markedly reduced by treatment with probenecid, suggesting that the renal excretion of M17055 is controlled predominantly by an active secretion mechanism. 5. The results show that M17055 is unlikely to cause or undergo significant pharmacokinetic interactions with concomitant drugs in metabolism and distribution. However, when it is administered simultaneously with certain organic anions, drug-drug interactions during kidney excretion may be possible.

Determination of lomefloxacin by terbium sensitized chemiluminescence method

A simple, rapid and sensitive chemiluminescence (CL) method was proposed for the determination of lomefloxacin (LFX). This method is based on the fact that the weak CL from the redox reaction of Ce(4+)-Na(2)SO(3) can be greatly enhanced by the complex of Tb(3+)-LFX. The CL intensity is directly proportional to the concentration of LFX in the range 2.0x10(-9) to 1.0x10(-5) mol L(-1), and the detection limit (S/N=3) is 1.1x10(-9) mol L(-1). This method has been applied to the detection of LFX in pharmaceutical preparation, urine and serum samples. Recoveries were in the range 95-105%. The CL mechanism of Ce(4+)-Na(2)SO(3)-Tb(3+)-LFX system was proposed to be an intermolecular energy transfer from excited SO(2)(*) to LFX and an intramolecular energy transfer from LFX to Tb(3+).

The pharmacokinetics of toborinone in subjects with congestive heart failure and concomitant renal impairment and/or concomitant hepatic impairment

The pharmacokinetics of toborinone was studied in subjects with congestive heart failure (CHF) and concomitant renal and/or hepatic disease. At the time of admission, subjects were grouped based on estimated creatinine clearance and serum bilirubin. Glomerular filtration rate was assessed using iothalamate clearance. Hepatic function was assessed using the caffeine metabolism test and indocyanine green clearance. No significant differences were observed in mean toborinone pharmacokinetic parameters among the four study groups. Positive correlations were observed between toborinone clearance and the measured indices of renal and hepatic function: creatinine clearance, iothalamate renal clearance, paraxanthine/caffeine ratio, and indocyanine green clearance. Toborinone clearance decreased with decreasing creatinine clearance, decreasing glomerular filtration rate, decreasing demethylation metabolic activity, and decreasing hepatic bloodflow, although no significant differences were observed in any mean toborinone pharmacokinetic parameters evaluated among the four study groups.

Determination of bioequivalence of lomefloxacin tablets using urinary excretion data

The present study describes development of a sensitive and simple HPTLC method for estimation of lomefloxacin (LMF) in human urine. The drug was extracted using chloroform after adjusting the pH of urine to 7.0. Chloroform extract was spotted on silica gel 60 F(254) TLC plate and was developed in a mixture of n-butanol-methanol-ethyl acetate-6 M ammonia (4:2:3:2, v/v/v/v) as the mobile phase and scanned at 290 nm. The peak for LMF resolved at R(F) of 0.40+/-0.02. The method was validated in terms of linearity (50-600 microgram/ml), precision, specificity and accuracy. The limit of detection and limit of quantification for LMF in urine were found to be 20 and 50 microgram/ml, respectively. The average recovery of LMF from urine was 91.93%. The proposed method was applied to generate urinary excretion data for LMF after administration of two market LMF tablet formulations (400 mg, Formulation R and Formulation T) to six healthy human volunteers in a two-treatment, open, crossover design. Various pharmacokinetic parameters like peak excretion rate ((dAU/dt)(max)), time for peak excretion rate (t(max)), AUC(0-48), AUC(0- infinity ), cumulative amount and % cumulative amount of LMF excreted, elimination half-life (t(1/2)), terminal elimination rate constant (k(el)) and overall elimination rate constant (K), were calculated for both the formulations. The average cumulative amounts of LMF excreted in urine after administration of Formulation R and Formulation T were found to be 321.60 mg (80.40% of dose) and 296.51 mg (74.13% of dose), respectively. The urinary excretion profiles of LMF upto 48 h for both the formulations were found to be similar. Statistical comparison (90% confidence intervals of ratio) of various pharmacokinetic parameters of Formulation T with that of Formulation R revealed that Formulation T is bioequivalent with Formulation R.

[Study on the direct determination of lomefloxacin in urine by derivative-synchronous fluorescence]

The LMX fluorescence properties at various pH of media were studied. The experiments indicated that LMX fluorescence emission wavelength is red shifted 40 nm at pH value of 3.3. The background interference was eliminated effectively. Under this condition, a new method for the determination of lomefloxacin in human urine by derivative-synchronous fluorescence has been developed. The linear equation of LMX can be obtained as dF/d lambda = -6.642c-24.143, of which the correlation coefficient is 0.9996. When concentrations of LMX were within the range of 0.35-28.10 mg.L-1, there exists a good linear relationship between the concentration and fluorescence intensity of LMX. The detection limit was 0.35 mg.L-1. The average recoveries of LMX were 97%-104% and the RSD were 0.83%-1.62%.

Differential-pulse adsorptive stripping voltammetric determination of the antibacterial lomefloxacin

A differential-pulse adsorptive stripping voltammetric method for the determination of trace amounts of the antibacterial lomefloxacin is proposed. By using an accumulation potential of -0.30 V and a 2 min accumulation time, the linear concentration range of application was 1.0-10.0 ng ml(-1) of lomefloxacin, with a relative standard deviation of 3.8% (for a level of 5.0 ng ml(-1)) and a detection limit of 0.3 ng ml(-1). The method was applied to determination of lomefloxacin in human urine and serum samples. It was validated using HPLC as a reference method. Recovery levels of the method reached 100% in all cases.

Voltammetric behavior and analytical applications of lomefloxacin, an antibacterial fluorquinolone

Lomefloxacin was reduced on a dropping mercury electrode, producing one or more peaks, depending on the pH of the aqueous medium. Coulometric measurements gave an experimental value of 1 electron for the main peak. Electrolysis was followed by UV spectrophotometry and liquid chromatography (LC), showing that a new band at 413 nm appeared for the electrolysis product in an acidic medium. Furthermore, by using UV spectrophotometry, an apparent pKa value of 6.75 +/- 0.05 was obtained for lomefloxacin corresponding to the carboxyl moiety in the 3-position. For analytical studies, the differential pulse polarographic mode in 0.1 N HCl was selected. The repeatability and reproducibility of the method were adequate (coefficient of variation [CV], 0.51%). The calibration curve method was used for the lomefloxacin concentration range of 7.0 x 10(-6) to 7.0 x 10(-5)M. The detection and quantitation limits were 1.0 x 10(-6) and 6.9 x 10(-6)M, respectively. For purposes of comparison, both UV spectrophotometric and LC (with UV and fluorimetric detection) methods were developed. The polarographic method showed good selectivity with respect to both excipients and degradation products. The recovery study showed a CV of <2% and an average recovery of 99.5% and it was not necessary to treat the sample before analysis. The method was applied to the determination of the uniformity content of lomefloxacin commercial tablets. The polarographic method was also successfully applied to the quantitation of lomefloxacin in urine, and the renal excretion profile was also determined.

Voltammetric analysis of certain 4-quinolones in pharmaceuticals and biological fluids

The voltammetric behaviour of Enrofloxacin (I), Sparfloxacin (II) and Fleroxacin (III) was studied using direct current (DCt), differential pulse (DPP) and alternating current (ACt). All the drugs manifest cathodic waves in Britton Robinson buffer over the pH range of 4.0-11.98. The waves were characterized as being irreversible, diffusion-controlled with limited adsorption properties. The diffusion current concentration relationships were found to be rectilinear over the ranges 4 x 10(-5) x 10(-4) M, 1 x 10(-5)-2 x 10(-4) M, 1 x 10(-5)-4 x 10(-4) M using DCt mode for I, II and III, respectively and 1 x 10(-6)-4 x 10(-5) M, 1 x 10(-6)-1 x 10(-4) M, and 2 x 10(-6)-8 x 10(-5) M, using DPP mode for I, II and III respectively, with minimum detectability (S/N = 3) of 1 x 10(-7) M for I, II and 2 x 10(-7) M for III. The proposed method was successfully applied to the determination of the studied compounds either per se or in formulations and biological fluids. The results obtained were concordant to those given using reference methods.

Complexation of antibacterial quinolonic acid and cinolonic derivatives with Zn(II) and Al(III): application to their determination in human urine

Nalidixic acid, 7-hydroxymethylnalidixic acid, oxolinic acid, pipemidic acid and cinoxacine form complexes with zinc(II) in the presence of acetate buffer of pH 5.5 and oxolinic acid, pipemidic acid and cinoxacine form complexes with aluminium(III) in the presence of chloroacetate buffer of pH 3.0. In all cases, an enhancement of the fluorescence emission was observed. Fluorimetric studies on the spectral characteristics of the complexes were performed. A 1:1 stoichiometry for all the complexes was established. The association constants were calculated, by using the changes in the fluorescence of all antibacterials, that occurred when the complexes were formed. The fluorescence reactions were used to develop methods for the determination of all of the above compounds, showing a higher sensitivity than in the absence of the cationic ions. The methods were satisfactorily applied to the determination of these compounds in urine.

Spectrofluorimetric analysis of certain 4-quinolone in pharmaceuticals and biological fluids

A highly sensitive spectrofluorimetric procedure is developed for the analysis of certain 4-quinolone antibiotics: sparfloxacin (I), oxolonic acid (II), flumequine (III) and enrofloxacin (IV) in their pharmaceutical dosage forms or in biological fluids. This procedure is based upon the intrinsic fluorescence in acetonitrile for sparfloxacin or upon the highly enhanced fluorescence obtained by the interaction of the drugs with AlCl3. The optimum pH for the maximum fluorescence intensity is 8-8.5 for I, 5-6 for II, III and pH 3.5 for IV. The different experimental parameters that affect the fluorescence intensity were carefully studied and incorporated into the procedure.

Pharmacokinetics and urinary excretion of DW116, a new fluoroquinolone antibacterial agent, in humans as a phase I study

Pharmacokinetics and urinary excretion of the new fluoroquinolone antibacterial agent DW116 [1-(5-fluoro-2-pyridyl)-6-fluoro-7-(4-methyl-1-piperazynyl)-1, 4-dihydro-4-oxoquinolone-3-carboxylic acid, hydrochloride] following oral administration (200, 400, 600 mg) were studied in humans as a phase I study. The plasma concentration of DW116 declined monoexponentially with a half-life range of 16-22 hr. The area under the curve (AUC) and Cmax increased proportionally as the dose increased. The T1/2 and mean residence time (MRT) (28.3-30.9 hr) were independent of dose. The Tmax appeared within 3 hr (0.9-2.7 hr) after drug administration. The Ka ranged from 1.3 to 4.1 (hr-1). The plasma half-life was much longer, and Cmax was higher by about two- to three-fold than conventional fluoroquinolones. Urinary recovery of DW116 was 29.6-61.6% of the dose. The maximum excretion rate appeared within 4 hr and decreased continuously after drug administration. A urinary metabolite was not detected in the urine extract obtained before and after hydrolysis by beta-glucuronidase (from Escherichia coli); this was different from other fluoroquinolone antibacterial agents. Poor metabolism in the kidney may contribute to the good oral bioavailability, but due to the low recovery (< 60%) in urine, it is possible that DW116 is metabolized in the liver or other organs.

Sparfloxacin pharmacokinetics in healthy volunteers: the influence of acidification and alkalinization

OBJECTIVE

To investigate the effect of acidification and alkalinization on the pharmacokinetics of sparfloxacin in healthy subjects.

METHODS

A single 200-mg oral dose of sparfloxacin was given to nine healthy Japanese volunteers on three separate occasions under different conditions of urinary pH. Acidic and alkaline conditions were achieved by repeated oral doses of ammonium chloride and sodium bicarbonate, respectively. The concentrations of sparfloxacin and its metabolite in plasma and urine were determined by high-performance liquid chromatography assays.

RESULTS

The difference between treatments for Cmax, AUCinfinity, and CL x f(-1) were found to be significant. The relative bioavailability of sparfloxacin was 84.4% and 122.3% after ammonium chloride and sodium bicarbonate treatments, respectively. The amount of unchanged sparfloxacin in urine samples collected 0-48 h after sparfloxacin administration represented 10.1% of the dose in the control, 14.3% of the dose in urine acidification and 8.4% of the dose with alkalinization of urine. Renal clearance was found to depend on urinary pH. However, the plasma elimination and the metabolism of sparfloxacin were not significantly altered by acidification or alkalinization of the urine.

CONCLUSION

The urinary pH dependence of the renal clearance of sparfloxacin will be of minor clinical importance with regard to the low contribution of renal excretion to the overall elimination of sparfloxacin. On the other hand, the alteration in the environmental pH in the gastrointestinal tract, produced by the concomitant ingestion of ammonium chloride or sodium bicarbonate, influences the absorption and bioavailability of sparfloxacin. This effect is likely to be clinically significant.

Pharmacokinetics and inflammatory fluid penetration of clinafloxacin

A single 200-mg dose of clinafloxacin was given orally to each of nine healthy male volunteers, and the concentrations of the drug were measured in plasma, cantharidin-induced inflammatory fluid, and urine over the following 24 h (48 h in the case of urine). The mean maximum concentration in plasma was 1.34 microg/ml at a mean time of 1.8 h postdose. The mean maximum concentration in the inflammatory fluid was 1.3 microg/ml at 3.8 h postdose. The mean elimination half-life of clinafloxacin in plasma was 5.65 h. The overall penetration into the inflammatory fluid was 93.1%, as assessed by determining the ratio of area under the concentration-time curves. Recovery of clinafloxacin in urine was 58.8% by 24 h and 71.8% by 48 h postdose.

Effect of renal impairment on the pharmacokinetics of grepafloxacin

Grepafloxacin is mainly (approximately 90%) excreted by nonrenal mechanisms. The effect of renal impairment on the pharmacokinetics of grepafloxacin was evaluated in an open-label study involving 20 adults, 15 of whom had some degree of renal impairment (creatinine clearance 7.5 to 64.0 ml/min). Of these 15, 3 had mild renal impairment, 6 had moderate renal impairment, and 6 had severe renal impairment. Grepafloxacin 400 mg was administered orally once daily for 7 days, and pharmacokinetic parameters were measured on days 1 and 7. The results show that both renal clearance and the amount of grepafloxacin excreted unchanged in urine, on day 1 and day 7, were significantly lower in individuals with severe renal impairment compared with those who were healthy. Renal clearance was 0.50 +/- 0.05 ml/min/kg in healthy individuals vs 0.15 +/- 0.05 ml/min/kg in patients with severe renal impairment on day 1, while the corresponding values on day 7 were 0.46 +/- 0.04 ml/min/kg vs 0.14 +/- 0.08 ml/min/kg, respectively. The percentage of grepafloxacin excreted unchanged in urine on day 1 was 5.1 +/- 3.0 in the healthy individuals and 1.5 +/- 0.7 in those with severe renal impairment. On day 7, the corresponding values were 7.9 +/- 1.9 and 2.9 +/- 2.2. No other significant pharmacokinetic differences occurred between the 2 groups. Accumulation during multiple dose administration did not vary with the degree of renal impairment. We conclude that the pharmacokinetics of grepafloxacin are not significantly different in individuals with varying degrees of renal impairment. Hence, dose adjustment is not necessary during treatment of patients with renal dysfunction.

Theophylline and warfarin interaction studies with grepafloxacin

Two phase I trials, each involving 16 healthy adult volunteers, were performed to investigate possible interactions between grepafloxacin and theophylline or warfarin. In the theophylline study, grepafloxacin 600 mg was administered once daily for 10 days to 12 volunteers who were receiving a maintenance dose of theophylline. This dose of theophylline was designed to produce mean serum theophylline concentrations of 7.5 mg/L; 4 volunteers received theophylline plus placebo. Pharmacokinetic parameters of theophylline were determined before grepafloxacin treatment and on day 10 of grepafloxacin or placebo administration. Peak theophylline concentrations and the area under the concentration-time curve increased significantly during grepafloxacin treatment, and apparent total clearance of theophylline was reduced by approximately 50%. No changes were observed in the placebo group and theophylline appeared to have no effect on the pharmacokinetics of grepafloxacin. In the warfarin study, grepafloxacin 600 mg was given once daily for 14 days to volunteers receiving a maintenance dose of warfarin. Warfarin was discontinued during the last 4 days of grepafloxacin administration. The pharmacodynamics of warfarin did not change after administration of grepafloxacin. Similarly, warfarin had no significant effect on the pharmacokinetics of grepafloxacin. We conclude that during treatment with grepafloxacin maintenance, doses of theophylline should be reduced by 50%, and we recommend that serum concentrations of theophylline be monitored during treatment with grepafloxacin. However, no dose adjustment is necessary for grepafloxacin when it is coadministered with theophylline, and dose adjustment does not seem to be required in concomitant treatment with grepafloxacin and warfarin.

Pharmacokinetics of sparfloxacin and interaction with cisapride and sucralfate

In an open, randomized, triple crossover study, the effects of cisapride and sucralfate on the pharmacokinetics of sparfloxacin were assessed. Fifteen healthy volunteers received 400 mg of sparfloxacin as a single oral dose on day 0. In a random order, concomitant doses of 10 mg of cisapride three times daily from day -2 to day 2 and 1 g of sucralfate four times daily from day -2 to day 0 were administered. Sparfloxacin concentrations were measured by bioassay and high-performance liquid chromatography. Pharmacokinetic parameters for sparfloxacin alone were as follows (mean +/- standard deviation): maximum concentration of drug in serum (C(max)), 1.27 +/- 0.39 microg/ml; time to C(max) (T(max)), 4.1 +/- 1.9 h; area under the concentration-time curve (AUC), 35.0 +/- 9.7 microg x h/ml; mean residence time, 28.5 +/- 5.7 h; half-life (t1/2), 20 +/- 4 h; urinary recovery (UR x f), 11.0% +/- 2.7%; and metabolite-sparfloxacin ratio in urine, 2.6. For the cisapride group there was a significant decrease in the sparfloxacin T(max) (1.9 +/- 2.1 h) and a significant increase in C(max) (1.74 +/- 0.73 microg/ml). The QTc interval for patients receiving sparfloxacin and cisapride was prolonged by 7.7% compared to the QTc interval during medication-free periods. Significant differences in the values for the group receiving sucralfate compared to the values for the group receiving sparfloxacin alone were found: C(max), 0.77 +/- 0.31 microg/ml; AUC, 18.6 +/- 5.8 microg x h/ml; t1/2, 26 +/- 10 h; and UR x f, 5.8 +/- 1.8%. Concomitant adminstration of cisapride accelerates the absorption and increases the peak concentration of sparfloxacin without having a significant effect on the extent of bioavailability. Coadministration of sucralfate leads to a 44% decrease in the bioavailability of sparfloxacin.

Biotransformation of the novel inotropic agent toborinone (OPC-18790) in rats and dogs. Evidence for the formation of novel glutathione and two cysteine conjugates

The metabolism of toborinone, (+/-)-6-[3-(3,4-dimethoxybenzylamino)-2-hydroxypropoxy]-2(1H)-quin - olinone, a novel inotropic agent, was studied in rats and dogs after intravenous administration. Chemical structures of the 13 metabolites were characterized by direct-probe FAB/MS and field desorption/MS, LC/FAB/MS, and various NMR measurements. After intravenous dosing of 10 mg/kg [14C]toborinone, fecal and urinary recoveries of the 14C dose were approximately 70% and 26-30%, respectively, in both rats and dogs. The predominant component of radioactivity was the unchanged toborinone in every biological specimen in rats and dogs. Although unchanged toborinone was predominantly observed, toborinone underwent extensive conjugations with glucuronic acid, sulfate, and glutathione, either directly or following phase I reaction. Metabolites resulting from oxidative N-C cleavage were minor both in number and in quantity in every biological specimen in rats and dogs. In rats, toborinone underwent O-demethylation to form M-7 and successive phase it reaction to yield the glucuronide M-1 and the sulfoconjugate M-2, and deconjugation to yield M-7, which was a primary metabolite accounted for 35.67% of the radioactivity excreted in the feces by 48 hr. Conjugates M-1 and M-2 were the major metabolites in rat plasma. In dogs, toborinone was metabolized via mercapturic acid pathway to yield the primary metabolites, cysteine conjugates M-10 and M-11 that accounted for 19.10% and 6.70% of the radioactivity excreted in the feces by 48 hr and that were detected species specifically in dogs. The glutathione conjugate M-13, which was isolated from in vitro incubations using dog liver, led us to consider a possible mercapturic acid pathway from the parent compound to M-10. Metabolites in dog plasma and those in urine in both rats and dogs were minor in quantity. The metabolic pathways of toborinone in rats and dogs are proposed herein.

Suspicion of quinolone active metabolite following discrepancy between predicted and experimental urine bactericidal activities

The prediction of urine antibacterial activity from pharmacological and microbiological parameters was assessed by using experimental urine levels and urine bactericidal titers determined up to 72 h after a 400-mg single dose of two quinolones in a phase I study. The area under the bactericidal curve (AUBC) was accurately predicted for norfloxacin but significantly (P < 0.001) underestimated for rufloxacin (actual value was four times higher than the predicted value against Escherichia coli and two times higher against Staphylococcus aureus). In vitro susceptibility differences between the two strains predicted the ex vivo AUBC differences for norfloxacin but not for rufloxacin, where ex vivo differences were greater than expected. Urine bactericidal titers for up to 72 h were accurately predicted for norfloxacin against E. coli and S. aureus and for rufloxacin against S. aureus, but experimental activity for up to 48 h was four times higher (P < 0.001) than the predicted activity for rufloxacin against E. coli. In the case of norfloxacin, the duration of adequate urine antibacterial activity against S. aureus was overestimated. Inaccurate estimations of ex vivo antibacterial activity of a suspected active metabolite (as with rufloxacin) when an adequate cutoff is not established may have dosing implications.

Comparative study of pharmacokinetics of two new fluoroquinolones, balofloxacin and grepafloxacin, in elderly subjects

Comparative pharmacokinetics and tolerability were studied in healthy elderly volunteers for two new fluoroquinolones, balofloxacin (Q-35) and grepafloxacin (OPC-17116), the main excretion routes being the renal and hepatic routes, respectively. Both agents were well tolerated in elderly subjects. In comparison with previously reported data from healthy younger adults, the absorption of balofloxacin was slightly delayed and urinary excretion was delayed and diminished. As a significant linear correlation was observed between renal clearance of balofloxacin and creatinine clearance, the delayed and diminished urinary recovery was attributed to the reduced renal function of the elderly subjects enrolled in the study. The absorption of grepafloxacin was also delayed, and the maximum plasma drug concentration and area under the plasma drug concentration-time curve were increased in the elderly by 31 and 48%, respectively, over those in younger adults on the basis of dose normalized to body weight. The plasma terminal elimination half-life and urinary recovery remained unchanged. Decreases in distribution volume and total body clearance in the elderly were considered to be the primary factors contributing to these differences.

Effect of ranitidine on renal clearance of lomefloxacin

OBJECTIVE

To examine the effect of ranitidine on the renal clearance of lomefloxacin.

SETTING

Department of Clinical Pharmacology, Jichi Medical School.

METHODS

Lomefloxacin 200 mg and ranitidine 300 mg or its placebo were given orally in a randomised, double-blind, crossover design. Blood and urine samples were obtained during a 24-h period after dosing.

RESULTS

The area under the plasma concentration-time curve and the elimination half-life of lomefloxacin were significantly increased following coadministration with ranitidine. These effects were caused by significant decreases in total (7.8%) and renal (22%) clearance of lomefloxacin. In contrast, creatinine clearance and urinary excretion of electrolytes were not influenced by ranitidine.

CONCLUSION

As lomefloxacin and ranitidine are excreted in urine by renal tubular secretion, the present results suggest that the renal tubular secretion of lomefloxacin is diminished by ranitidine. As the reduction in lomefloxacin clearance is only marginal, it is probable that the drug interaction observed in this study is not of clinical significance.

One-month oral toxicity study of the new quinolone antibacterial agent (S)-10-[(S)-(8-amino-6-azaspiro[3,4]octan-6-yl)-9-fluoro-2,3-dihydro-3- methyl-7-oxo-7H-pyrido [1,2,3-de] [1,4] benzoxazine-6-carboxylic acid hemihydrate in rats and cynomolgus monkeys

One-month oral toxicity of (S)-10-[(S)-(8-amino-6-azaspiro[3,4] octan-6-yl)]-9-fluoro-2,3-dihydro-3-methyl-7-oxo-7H-pyrido[1,2,3-de] [1,4]benzoxazine-6-carboxylic acid hemihydrate (CAS 151390-79-3, DV-7751a) a new quinolone antibacterial agent was investigated in Sprague-Dawley rats at doses of 12.5, 50, 200 and 800 mg/kg/d and in cynomolgus monkeys at 10, 30 and 100 mg/kg/d. Rats receiving 200 mg/ kg showed abnormal urine crystals, enhanced deposition of lipid in hepatocytes and exacerbation of osteochondrotic lesions in the femoral condyle. In addition, dosing at 800 mg/kg induced decrease in body weight gain and increased levels of serum alkaline phosphatase (ALP), cholinesterase, leucine aminopeptidase and total cholesterol. Monkeys receiving 100 mg/kg showed abnormal urine crystals and increases in serum glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and ALP levels. The non-toxic doses of DV-7751a in rats and monkeys were 50 and 30 mg/kg, respectively, under the present experimental conditions.

Effect of probenecid and ranitidine on urinary excretion of lomefloxacin in rats

To examine the renal tubular transport pathways of lomefloxacin, a new quinolone antibiotic, the agent was injected intravenously with or without pretreatment with probenecid, an organic anion, or ranitidine, an organic cation, in rats. Urinary excretion of lomefloxacin significantly decreased in the probenecid-treated animals. However, no significant decrease was observed in this parameter by pretreatment with ranitidine. These results suggest that lomefloxacin is mainly secreted in urine by the organic anion transport system, while the pathway mediated by the organic cation transport system is negligible.

[A 4-week oral toxicity study of prulifloxacin (NM441) in rats followed by a 4-week recovery test]

A repeated dose toxicity study of prulifloxacin, a new antibacterial agent, was conducted in Sprague-Dawley rats. Male and female rats were given the test material orally for 4 weeks at doses of 0 (control), 30, 300 and 3000 mg/kg. After discontinuation of the treatment, a 4-week recovery test was also conducted. There was one case of death in the 3000 mg/kg group. Grayish green and soft feces, unkempt fur, transient deep respiration and decreased body weight gain were observed in the 3000 mg/kg group. Decreased food consumption and increased water intake were seen in the 300 and 3000 mg/kg groups. Ophthalmoscopic examination failed to show any abnormalities related to the treatment. In urinalysis, crystalline substance in the urinary sediments, cloudy urine and decreased Na+ excretion were observed in the 300 and 3000 mg/kg groups. Increased urine volume, lowered urine specific gravity and decreased K+ and Cl- excretions were seen in the 3000 mg/kg group. Hematologic examination showed decreased Hb, Ht, MCV and MCH and increased WBC in the 3000 mg/kg group. Blood chemical examination revealed increased BUN and decreased K+ and Cl- in the 3000 mg/kg group, and decreased K+ and gamma-globulin in the 300 mg/kg group. Pathological changes caused by the treatment were as follows. Cecal weight was increased in all dose groups. Cecal distention and swelling of its absorptive cells were seen in the 300 and 3000 mg/kg groups. In kidney, tubular nephrosis with crystalline substance was observed in the 300 and 3000 mg/kg groups, and its organ weight was increased in the 3000 mg/kg group. The above-mentioned changes were reversible except for decreased gamma-globulin, increased BUN and urine volume, and lowered urine specific gravity. Ulcer and small cavities associated with proliferation of fibrous tissue in the femoral articular cartilage were observed in the 3000 mg/kg group at the end of recovery period of 4 weeks. Plasma levels and urinary concentrations of active metabolite of the test material were increased in all dose groups with dose-related manner, whereby no sex difference was observed. No effects caused by the repeated dosing were seen in the plasma concentrations. Increased cecal weight in the 30 mg/kg group was considered to be attributable to the pharmacological effect of the test material. The results show that the NOAEL of prulifloxacin is 30 mg/kg for 4-week repeated dose toxicity in rats.

[Renal toxicity of prulifloxacin (NM441) in rats]

Renal toxicity of prulifloxacin, a new antibacterial agent, was investigated in rats of both sexes. The animals were given prulifloxacin orally for 28 days at a dose of 3000 mg/kg. Tubular nephrosis in which crystalline substances appeared primarily within tubules was observed from the second day of administration, and a large number of brown circular crystals were found in the urinary sediment from the first day of administration. Electron microscopic observation revealed a close resemblance of the ultrastructural characteristics between the intratubular crystalline substance and the urinary brown circular crystal, and the tubules were occasionally occluded by the crystalline substances. Infrared spectral analysis and X-ray microanalysis indicated that the brown circular crystal consisted of NM394, an active metabolite of prulifloxacin. These results suggested that NM394, which was filtered into the primary urine, may be precipitated as crystals on the process of water reabsorption in the tubules. And then most of the crystals would be washed out as crystalluria particles, and some of crystals retained and caused the obstructive uropathy.

[A 4-week oral toxicity study of prulifloxacin (NM441) in dogs followed by a 4-week recovery test]

A repeated dose toxicity study of prulifloxacin, a new antibacterial agent, was conducted in beagle dogs. Male and female dogs were given the test material orally for 4 weeks at doses of 0 (control), 30, 150 and 750 mg/kg. After discontinuation of the treatment, a 4-week recovery test was also conducted. Feces containing white material were seen in the 150 and 750 mg/kg groups. Salivation, prone, lateral or sitting position, gait disturbance, and locomotor depression were observed in the 750 mg/kg group. In this dose group, decreased body weight and food and water consumptions were also observed. There were no treatment-related effects on survival. Ophthalmoscopic and electrocardiographic examinations and urinalysis failed to show any abnormalities related to the treatment. Hematologic examination showed decreased WBC in the 750 mg/kg group. Blood chemical examination revealed increased GPT and alpha 2-globulin in the 750 mg/kg group. Pathological changes caused by the treatment were as follows. Rarefaction of matrix, cavitations and erosions in humeral and femoral articular cartilages, and inflammatory cell infiltration in synovium were seen in the 150 and 750 mg/kg groups. Focal hemorrhage in synovium was also observed in the 750 mg/kg group. In kidney, regeneration of tubular epithelium, inflammatory cell infiltration, fibrosis and crystalline substance in the tubular lumen were observed in the 750 mg/kg group. The above-mentioned changes were satisfactorily reversible except for the changes in the humeral and femoral articular cartilages and in the kidney. Plasma levels and urinary concentrations of active metabolite of the test material were increased in all dose groups with dose-related manner, whereby no sex difference was observed. No effects caused by the repeated dosing were seen in the plasma concentrations. Toxicological findings were not observed in the 30 mg/kg group. The results show that the NOAEL of prulifloxacin is 30 mg/kg for 4-week repeated dose toxicity in dogs.

Single-dose rufloxacin versus 3-day norfloxacin treatment of uncomplicated cystitis: clinical evaluation and pharmacodynamic considerations

The efficacy and safety of rufloxacin (400 mg, single dose) were compared to those of norfloxacin (400 mg twice a day for 3 days) for the treatment of women with uncomplicated cystitis. In addition, urine levels, drug level/MIC ratio, and urine antibacterial activity 72 to 84 h after treatment initiation were determined in a subgroup of patients for pharmacodynamic assessment. A total of 203 women were included and treated in this open, randomized clinical trial; 100 patients received norfloxacin, whereas 103 received rufloxacin. Of these, 156 (74 and 82 patients in the norfloxacin and rufloxacin groups, respectively) were considered bacteriologically evaluable. At the first follow-up visits (3 to 12 days after starting the treatment), bacteriological cure rates were 99 and 94% for norfloxacin and rufloxacin, respectively. Seventy-nine percent (119 of 150) of bacteriologically cured patients attended a long-term follow-up visit (4 to 6 weeks after starting the treatment), where a relapse rate of 4% (2 of 54) and 5% (3 of 64) were found in the norfloxacin and rufloxacin groups, respectively. The pharmacodynamic evaluation performed in 35 patients showed similar median urine levels (approximately equal to 25 micrograms/ml) and urine antibacterial activity for both treatment groups against initial isolates, despite a higher norfloxacin level/MIC ratio due to the lower MIC of norfloxacin. Twenty-one patients (20%) in the rufloxacin group and 12 patients (12%) in the norfloxacin group reported 39 and 16 adverse events, respectively, almost all of them being mild and lasting < 24 h. Overall, gastrointestinal reactions were the most frequent adverse events reported. However, 12 patients treated with rufloxacin reported 15 central nervous system adverse events. This study shows that single doses of rufloxacin are as effective as a norfloxacin 3-day standard treatment in uncomplicated cystitis. The results obtained with rufloxacin are consistent with its pharmacodynamic properties.

Pharmacokinetics of marbofloxacin in dogs after oral and parenteral administration

Six dogs were treated with a single intravenous (i.v.) dose (2 mg/kg) of marbofloxacin, followed by single oral (p.o.) doses of marbofloxacin at 1, 2 and 4 mg/kg, according to a three-way crossover design. The same experimental design was used for the subcutaneous (s.c.) route. In addition, a long-term trial involving eight dogs given oral doses of marbofloxacin at 2, 4 and 6 mg/kg/day for thirteen weeks was carried out. Plasma and urine samples were collected during the first two trials, plasma and skin samples were collected after the second of these trials. Plasma, urine and skin concentrations of marbofloxacin were determined by a reverse phase liquid chromatographic method. Mean pharmacokinetic parameters after i.v. administration were the following: t1/2 beta = 12.4 h; ClB = 0.10 L/h.kg; Varea = 1.9 L/kg. The oral bioavailability of marbofloxacin was close to 100% for the three doses. At 2 mg/kg, Cmax of 1.4 micrograms/mliter was reached at tmax of 2.5 h. Mean AUC and Cmax values had a statistically significant linear relationship with the doses administered. About 40% of the administered dose was excreted in urine as unchanged parent drug. After s.c. administration, the calculated parameters were close to those obtained after oral administration, except tmax (about 1 h) which was shorter. The mean skin to plasma concentration ratio after the long-term trial was 1.6, suggesting good tissue penetration of marbofloxacin.

Ex vivo antibacterial properties of rufloxacin compared with those of norfloxacin in a study with healthy volunteers

Twelve adult males participated in a randomized crossover phase I clinical trial comparing serum bactericidal titers (SBTs), urine bactericidal titers (UBTs), and urine killing rates (UKRs) against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, after the administration of single 400-mg doses of rufloxacin and norfloxacin at different times up to 72 h postdose. SBTs were significantly higher (P < 0.05) against E. coli from 8 to 48 h and against S. aureus from 4 to 24 h with rufloxacin. UBTs for E. coli were higher (P < 0.05) for norfloxacin at early sample times (0 to 8 h) but higher for rufloxacin (P < 0.05) at sample times from 16 h on for both E. coli and S. aureus. Similar UKRs were obtained for both quinolones for 0 to 2 h and 8 to 12 h, but the UKR was maintained for 72 h with rufloxacin. The high and sustained mean levels of rufloxacin in urine (> 35 micrograms/ml), median UBTs (> 32 for E. coli and 16 for S. aureus) and UKRs for E. coli suggest prolonged urine antibacterial activity (for at least 72 h) and its use as a single 400-mg dose in the treatment of uncomplicated cystitis.

Antibacterial activity of marbofloxacin. A new fluoroquinolone for veterinary use against canine and feline isolates

Marbofloxacin is a new fluoroquinolone developed exclusively for veterinary use. Minimum inhibitory concentrations of marbofloxacin were assessed for 816 recent isolates associated with canine or feline diseases. Marbofloxacin showed a broad spectrum of activity against gram-negative and gram-positive bacteria. In vitro rates of killing of marbofloxacin and enrofloxacin were compared against strains of Staphylococcus intermedius and Pasteurella multocida, and the results showed no marked difference between the two antibiotics. The duration of bactericidal activity was evaluated ex vivo in the urine of dogs and cats treated with marbofloxacin and lasted from 2 to 5 days after a single administration according to the dosages. Post-antibiotic effect durations were determined with Escherichia coli, Pasteurella multocida, Staphylococcus aureus and Staphylococcus intermedius and were found almost equal to those of enrofloxacin or ciprofloxacin. These results predict a great potential for marbofloxacin in the treatment of a wide range of diseases in dogs and cats.

Determination of the new fluoroquinolone balofloxacin and its metabolites in biological fluids by high performance liquid chromatography

A sensitive high performance liquid chromatographic method for the determination in biological fluids of 1-cyclopropyl-6-fluoro-1,4- dihydro-8-methoxy-7-(3-methylaminopiperidin-1-yl)-4-oxoquinoline-3 -carboxylic acid dihydrate (CAS 127294-70-6, balofloxacin, Q-35), a new fluoroquinolone, as well as its metabolites, has been developed. Balofloxacin and its metabolite, N-desmethyl balofloxacin, were separated and determined by reversed-phase column with fluorescence detection. Balofloxacin glucuronide was determined as balofloxacin after alkali hydrolysis. This method exhibited good precision and accuracy. Furthermore, it is a simple method and requires only a small amount of samples, and therefore should be useful for pharmacokinetic studies in animals and humans.

Design and optimization of the variables in the adsorptive stripping voltammetric determination of rufloxacin in tablets, human plasma and urine

An adsorptive stripping voltammetric method with a hanging mercury drop electrode was developed for the determination of the fluoroquinolone rufloxacin in tablets, human plasma and urine. Measurements were obtained in differential pulse mode and a multivariate strategy was used to optimize the variables involved. Besides the independent effects of the variables, a strong interaction between scan rate and pulse duration has been found. Rufloxacin was analysed at concentrations between 1.7 x 10(-8) and 1.9 x 10(-7) M with a detection limit of 9.2 x 10(-9) M. Diluted tablet solutions and urine samples were analysed directly, while plasma samples needed an extraction procedure before voltammetric analysis. An improved HPLC procedure was used as comparative method.

Determination of a new fluoroquinolone antimicrobial agent, (S)-10-[(S)-(8-amino-6-azaspiro d3,4]octan-6-yl)]-9-fluoro-2, 3-dihydro-3-methyl-7-oxo-7H-pyrido[1,2,3-de][1,4]benzoxazine-6- carboxylic acid hemihydrate, DV-7751a, in human serum and urine using solid-phase extraction and high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method for the determination of a new fluoroquinolone antimicrobial agent, (S)-10-[(S)-(8-amino-6-azaspiro[3,4]octan-6-yl)]-9-fluoro-2,3- dihydro-3-methyl-7-oxo-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid hemihydrate (DV-7751a, I) in human serum and urine has been developed. Compound I and the internal standard were extracted from serum and urine by means of Bond Elut C8 LRC column. The extracts were chromatographed on a reversed-phase Inertsil ODS-2 column using tetrahydrofuran-50 mM KH2PO4 (pH2)-1 M ammonium acetate (19:81:1, v/v) as the mobile phase at a flow-rate of 1.0 ml/min. Fluorescence detection at an excitation wavelength of 305 nm and an emission wavelength of 530 nm resulted in a limit of quantitation of 0.0098 microgram/ml for serum and 0.098 microgram/ml for urine. The method showed satisfactory sensitivity, precision, accuracy, recovery and selectivity. Stability studies showed that I was stable in serum and urine for at least 1 month at -20 degrees C and for at least 48 h at room temperature.

High-performance liquid chromatographic determination of the new quinolone antibacterial agent DU-6859a in human serum and urine using solid-phase extraction with photolysis-fluorescence detection

A sensitive and specific HPLC method for the determination of DU-6859a (I), a fluoroquinolone antibacterial agent, in human serum and urine was developed. Compound I and the internal standard extracted from serum and urine by means of a Bond Elut C8 LRC cartridge showed recoveries of 96%. The extracts were chromatographed on a reversed-phase column with photolysis-fluorescence detection. This unique detection method was 42.5 times more sensitive than intrinsic fluorescence detection, the limits of detection being in 3.43 ng/ml for serum and 4.35 ng/ml for urine. In addition, I was stable in serum and urine for at least 1 month at -20 degrees C. The proposed method was sensitive and selective enough to apply to pharmacokinetic studies of I in humans after a single oral dose of 100 mg.

Renal clearance of lomefloxacin is decreased by furosemide

The interaction between lomefloxacin, a new quinolone, and furosemide, a loop diuretic, has been examined. Oral lomefloxacin 200 mg and furosemide 40 mg were given together or separately to 8 healthy subjects, and blood and urine samples were obtained over the following 12 h. The plasma concentrations of lomefloxacin following coadministration with furosemide were higher than after lomefloxacin alone and its AUC was increased, and its total and renal clearances were decreased. No change in the pharmacokinetics of furosemide was found after coadministration of lomefloxacin. As quinolones and furosemide are reported to be excreted in urine by the renal tubular anion transport system, the present results suggest that the renal tubular secretion of lomefloxacin is diminished by furosemide. It is not clear whether this pharmacokinetic interaction might be clinically important.

Stereoselective high-performance liquid chromatographic assay for the determination of OPC-18790 enantiomers in human plasma and urine

A high-performance liquid chromatographic assay method for the quantification of OPC-18790 enantiomers in human plasma and urine is described. A human plasma or urine was extracted with organic solvent under alkaline conditions following the addition of internal standard. The enantiomers and internal standard were then derivatized by reaction with the chiral reagent GITC (2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate), followed by octadecylsilica chromatographic separation of the diastereomeric products. The mobile phase consisted of acetonitrile-water (41:59). The fluorescence of the eluate was monitored at 355/405 nm. The lowest quantification limit of each enantiomer was 10 ng/ml in plasma and 0.1 micrograms/ml in urine. Both intra- and inter-day coefficients of variation were below 10%. The assay is sensitive, specific and applicable for stereoselective pharmacokinetic studies in human.

Determination of BAY y 3118, a novel 4-quinolone, in biological fluids using high-performance liquid chromatography and photothermal post-column derivatization

A reversed-phase high-performance liquid chromatographic (HPLC) method that allows the sensitive and selective quantification of a novel 4-quinolone (BAY y 3118, I) in biological fluids is described. After sample dilution with 0.05 M phosphoric acid (plasma) or 0.1 M phosphate buffer pH 7.5 (urine), samples can be directly injected into the HPLC system. Prior to fluorescence detection, I is decomposed to fluorescence compound(s) by post-column derivatization utilizing either photolysis (Beam Boost reaction unit) or a combination of thermolysis and photolysis (laboratory-made post-column reactor). Compared with fluorescence detection alone, derivatization increases the signal intensity (about 80-fold) and the selectivity of the detection significantly. Concentrations down to 0.01 mg/l could be quantified in biological fluids. Only thermolysis was not able to decompose I to fluorescence products. Investigations on the stability of I in plasma and urine demonstrate good stability under the different conditions tested. The method was applied to human plasma and urine samples from a subject after a single oral dose of 100 mg of I.

Trace levels of pyrroloquinoline quinone in human and rat samples detected by gas chromatography/mass spectrometry

A detailed procedure for the assay of free pyrroloquinoline quinone (PQQ) in human and rat samples by gas chromatography/mass spectrometry (GC/MS) has been established with stable-isotopic PQQ as internal standard. PQQ was extracted from the samples, after addition of the internal standard, with butanol under acid conditions and with Sep-Pak C18 cartridges. After derivatization of PQQ with phenyltrimethylammonium hydroxide, molecular peaks at m/z 448 and 462 were used for detection of PQQ and [U-13C]PQQ by selected ion monitoring, respectively. Trace amounts of free PQQ were detected in eight organs, plasma and urine of the human, and in three organs of the rat. The PQQ level was highest in the human spleen (5.9 +/- 3.4 ng/g tissue, followed by the pancreas and lung, and it was below detection limits for human brain and heart. Trace levels of PQQ were also found in rat small intestine, liver and testis. Our data are far below those measured by the redox cycling method of Gallop's group for human plasma, adrenal and urine.

Determination of sparfloxacin in serum and urine by high-performance liquid chromatography

A specific and sensitive analytical method for the determination of sparfloxacin in serum and urine is described. Serum proteins are removed by precipitation with acetonitrile after the addition of ofloxacin as an internal standard. The supernatant solvent is evaporated in a vacuum concentrator and the dry residue is redissolved in the mobile phase. Separation is performed on a cation-exchange column (Nucleosil 100 5SA, 125 x 4.0 mm I.D., 5 microns particle size) protected by a guard column (Perisorb RP-18, 30 x 4.0 mm I.D., 30-40 microns particle diameter). The mobile phase consisted of 750 ml of acetonitrile and 250 ml of 100 mmol/l phosphoric acid (v/v) to which sodium hydroxide had been added. The final concentration of sodium was 23 mmol/l and the pH was 3.82. Sparfloxacin and ofloxacin were determined by spectrofluorimetry (excitation wavelength 295 nm; emission wavelength 525 nm). The flow-rate was 1.5 ml/min and the retention times were 4.7 (sparfloxacin) and 8.0 (ofloxacin) min. Validation of the method yielded the following results for serum: detection limit 0.05 mg/l; precision between series 10.4-3.6%; recovery 99.5-100.0%; comparison with a microbiological assay c(bioassay) = 1.035c(HPLC) - 0.06. The test organism was Bacillus subtilis ATCC 6633. For urine the results were: detection limit 0.5 mg/l; precision between series 7.8-5.0%; recovery 97.0-97.8%; method comparison c(bioassay) = 1.092c(HPLC) - 1.09. No interferences were observed in human volunteers. The method can also be applied to stool samples.

High-performance liquid chromatography and preliminary pharmacokinetics of rufloxacin and its metabolites, N-desmethylrufloxacin and rufloxacinsulfoxide, in urine of rhesus monkey Macaca mulatta

A gradient high-performance liquid chromatographic method for the quantification of rufloxacin and two of its metabolites in urine, N-desmethylrufloxacin and rufloxacinsulfoxide, has been developed and validated. Monkey urine samples were diluted ten times with distilled water and 20 microliters were injected onto a Cp Spher 5-ODS column, 5 microns particle size. The mobile phase was a mixture of 4% acetonitrile and 96% buffer at time 0, which changed linearly over 37 min to 26% acetonitrile and 74% buffer. Detection was achieved at 246 nm. The limit of detection of the three compounds was 0.50 microgram/ml. An example of a pharmacokinetic study of rufloxacin and its metabolites in monkeys is shown.