Application of non-linear angle synchronous spectrofluorimetry to the determination of complex mixtures of drugs in urine: a comparative study.

Synchronous fluorescence spectroscopy (SFS) is a rapid, sensitive and non-destructive method suitable for the analysis of multifluorophoric mixtures. In this study non linear variable angle synchronous spectrofluorimetry was applied to the determination of three fluoroquinololes in urine. Although this technique provides very good results, total resolution of multicomponent mixtures is not always achieved when the spectral profiles strongly overlap. Partial least-squares regression (PLS-1) was utilized to a develop calibration model that related synchronous fluorescence spectra to the analytical concentration of fluoroquinolones in the presence of urine. The same multicomponent mixture was determined using excitation emission matrix fluorescence (EEMF) along with N-way partial least squares regression (N-PLS and U-PLS). The determination was carried out in micellar medium 0.01 M with a pH of 4.8 provided by 0.2 M sodium acetate/acetic acid buffer. A central composite design was selected to obtain a calibration matrix of 25 standards plus a blank sample. The proposed methods were validated by application to a test set of synthetic samples. The results show that SFS with PLS-1 is a better method compared to EEMF with N-PLS or U-PLS because of the low RMSEP values of the former.

Pharmacokinetics of pefloxacin mesylate in human urine using capillary electrophoresis electrochemiluminescence detection.

A novel and simple method to determine pharmacokinetics of pefloxacin mesylate (PM) in urine of seven healthy adults was developed. The proposed methodology was based on the electrochemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium (II) at a platinum electrode. The ECL intensity was found greatly enhanced in the presence of PM, which could directly participate in the light-emitting reaction as the reductant (in former/unchanged form). Under optimised conditions, the calibration curve was linear from 0.02 to 12 mg/L with a detection limit of 0.004 mg/L (sigma=3). The RSD of the peak height was less than 2.4% (n=6). The recoveries in human urine were 96.2% to 98.3%. The highest excretion rate in urine was observed during the period 1.5-2 h after oral administration. The urinary excretion ratio of PM was 13.6% within 48 h.

Some pharmacokinetic parameters of pefloxacin in lactating goats.

The aim of this study was to elucidate some of the pharmacokinetic parameters of pefloxacin in lactating goats (n = 5) following intravenous (i.v.) or intramuscular (i.m.) injections of 10 mg/kg bw. Serially obtained serum, milk and urine samples were collected at precise time intervals, and the drug concentrations were assayed using a microbiological assay. A two-compartment open model best described the decrease of pefloxacin concentration in the serum after intravenous administration. The maximum serum concentration (C0(p)) was 8.4 +/- 0.48 microg/ml; elimination half-life (t 1/2 beta) was 1.6 +/- 0.3 h; total body clearance (Cl(tot) was 3.6 +/- 0.3 L/kg/h; steady-state volume of distribution (V(dss)) was 5.14 +/- 0.21 L/kg; and the area under the curve (AUC) was 2.78 +/- 0.22 microg.ml/h. Pefloxacin was absorbed rapidly after i.m. injection with an absorption half-life (t 1/2 ab) of 0.32 +/- 0.02 h. The peak serum concentration (Cmax) of 0.86 +/- 0.08 microg/ml was attained at 0.75 h (Tmax). The absolute bioavailability after i.m. administration was 70.63 +/- 1.13% and the serum protein-bound fraction ranged from 7.2% to 14.3%, with an average value of 9.8 +/- 1.6%. Penetration of pefloxacin from the blood into the milk was rapid and extensive, and the pefloxacin concentration in milk exceeded that in serum from 1 h after administration. The drug was detected in milk and urine for 10 and 72 h, respectively; no samples were taken after 72 h.

Selective separation and simultaneous determination of trace levels of five types of fluorinated quinolone drugs by thin-layer chromatography/fluorescence densitometry.

This paper reports the determination of trace levels of 5 types of fluorinated quinolone drugs, i.e., ciprofloxacin, norfloxacin, enoxacin, pefloxacin, and ofloxacin, by thin-layer chromatography (TLC)/fluorescence densitometry. The new analytical method uses 2-step TLC development, selective separation, and simultaneous determination of the 5 drugs. The method was also applied to the determination of recoveries of standards of the 5 drugs in plasma and urine samples. The results show that the method has a wide linear range, high repeatability, and good stability.

Disposition kinetics and urinary excretion of pefloxacin after intravenous injection in crossbred calves.

The disposition kinetics and urinary excretion of pefloxacin after a single intravenous administration of 5 mg/kg were investigated in crossbred calves and an appropriate dosage regimen was calculated. At 1 min after injection, the concentration of pefloxacin in the plasma was 18.95 +/- 0.892 microg/ml, which declined to 0.13 +/- 0.02 microg/ml at 10 h. The pefloxacin was rapidly distributed from the blood to the tissue compartment as shown by the high values for the initial distribution coefficient, alpha (12.1 +/- 1.21 h-1) and the constant for the rate of transfer of drug from the central to the peripheral compartment, K12 (8.49 +/- 0.99 h ). The elimination half-life and volume of distribution were 2.21+/- 0.111 h and 1.44 +/- 0.084 L/kg, respectively. The total body clearance (ClB) and the ratio of the drug present in the peripheral to that in the central compartment (P/C ratio) were 0.454 +/- 0.026 L/kg h) and 5.52 +/- 0.519, respectively. On the basis of the pharmacokinetic parameters obtained in the present study, an appropriate intravenous dosage regimen for pefloxacin in cattle for most of the bacteria sensitive to it would be 6.4 mg/kg repeated at 12 h intervals.

Urinary excretion and bactericidal activities of a single oral dose of 400 milligrams of fleroxacin versus a single oral dose of 800 milligrams of pefloxacin in healthy volunteers.

Twelve healthy volunteers participated in this randomized crossover study to compare the concentrations and recovery levels of fleroxacin and pefloxacin in urine and to assess their bactericidal activities against 12 strains of urinary pathogens with different susceptibilities over a wide range of MICs. The volunteers received a single oral dose of 400 mg of fleroxacin or 800 mg of pefloxacin. The mean cumulative renal excretion of unchanged fleroxacin, N-demethyl-fleroxacin, and N-oxide-fleroxacin accounted for 67, 7, and 6% of the total dose, respectively. The total urinary recovery of pefloxacin and the active metabolite norfloxacin was 34%. In the time-kill and the urinary bactericidal titer (UBT) studies, only the subjects' urine not supplemented with broth was used. With most tested organisms and both quinolones it took more than 8 h to achieve a reduction in CFU of 99.9% (3 log units). Overall, there was a good correlation between UBTs and MICs for the strains. Against Escherichia coli ATCC 25922 the median UBTs were similar for both antibiotics and at least 1:8 for 96 h; against the E. coli strain for which the MIC was 0.5 microgram/ml the UBT was at least 1:4 for 48 h. The UBTs of both drugs against Klebsiella pneumoniae were at least 1:16 for 72 h. The UBTs for Staphylococcus aureus (the MIC for which was 16 micrograms/ml) of both antibiotics were low, and in some of the samples, no bactericidal titers were observed. UBTs for Proteus mirabilis of pefloxacin are significantly higher than those of fleroxacin. For Pseudomonas aeruginosa the median UBTs were present for the 24-to-48-h interval. The same is true for Enterococcus faecalis. Against Staphylococcus saprophyticus, UBTs were present for at least 48 h with both quinolones. Overall, a single oral dose of 400 mg of fleroxacin exhibits UBTs comparable to those of 800 mg of pefloxacin. Therefore, it may be expected that half of the dose of fleroxacin gives comparable results in the treatment of urinary tract infections; this should be substantiated in comparative clinical trials.

[Study on fluorescence method of pefloxacin].

Pefloxacin is a new kind of antibiotic. In this paper, a sensitive fluorescence method has been developed for the analysis of Pefloxacin. It has stronger fluorescence excitation. The fluorescence of Pefloxacin was measured at excitation wavelength 282nm and emission wavelength 440nm. The method is highly sensitive with lower limit of detection, calibration curves were linear between 1 x 10(-9) - 1 x 10(-6)mol/L, with a regression coefficient of 0.9999. At the same time, recoveries of pefloxacin in Human serum Albumin and Urine are 95% and 105% respectively.

Urine bactericidal activity of pefloxacin versus norfloxacin in healthy female volunteers after a single 800-mg oral dose.

In an open randomised crossover study the antibacterial activity of pefloxacin and norfloxacin was assessed in the urine after a single 800-mg oral dose in 14 healthy female volunteers. Pefloxacin demonstrated lower peak concentrations in the urine than norfloxacin (mean, 217.2 mg/l versus 492.9 mg/l as determined by the microbiological assay) but pefloxacin was present over a longer period of time in sufficient concentrations than norfloxacin. Mean urine levels of at least 2 mg/l were present for 7 days after pefloxacin administration and 2 days after norfloxacin administration as determined by the microbiological assay. Overall, the urinary recovery of pefloxacin and norfloxacin amounted to 49.3% and 25.1%, respectively, of the total administered dose. The average urine bactericidal activity against the five test organisms was as follows: against reference strain Escherichia coli ATCC 25922 susceptible to nalidixic acid (Nal-S) for 5 days with pefloxacin and 2 days with norfloxacin; against three clinical isolates, one strain each of E. coli resistant to nalidixic acid (Nal-R), Klebsiella pneumoniae Nal-R, and Staphylococcus saprophyticus, for 3 days with pefloxacin and 24 h with norfloxacin; and against a clinical isolate of Enterococcus faecalis for 2 days with pefloxacin and 12 h with norfloxacin. In conclusion, pefloxacin as a single dose proved to have sufficiently high and long-lasting urine bactericidal activity against urinary pathogens. These findings support the results of a meta-analysis of seven clinical trials in patients with uncomplicated lower UTI, demonstrating a single oral dose of 800 mg pefloxacin to be as effective as a conventional treatment with comparative drugs.

Penetration of pefloxacin and its desmethyl metabolite into the uroepithelium after a 800-mg single oral dose in human patients.

Penetration of pefloxacin into the uroepithelium was studied in 20 patients (10 men and 10 women) receiving a single oral dose of 800 mg. Samples of serum, urine, and uroepithelium were taken 1.8 h (mean) after the dose. Pefloxacin and its active metabolite, norfloxacin, were assayed by liquid chromatography, and the microbiologically active compounds were quantified by a microbiological assay. Both procedures were correlated (r > 0.7); nevertheless, slight differences detected in concentrations depended on the levels of norfloxacin achieved in the biological samples. The serum and tissue concentrations were higher than the concentration of bactericide (4 micrograms.ml-1), except in one case. The uroepithelium concentration of pefloxacin was proportional to the serum concentration (r = 0.79). The urinary concentrations ranged from 1.2 micrograms.ml-1 to 82.4 micrograms.ml-1. The mean norfloxacin/pefloxacin ratios were 3% in serum, 8% in uroepithelium, and 44% in urine. The mean uroepithelium/serum concentration ratios were 1 for pefloxacin and 2.3 for norfloxacin. This result shows that, at a time close to that of the maximum concentration, there is good penetration of pefloxacin and norfloxacin into the uroepithelium.

Effect of an antacid containing magnesium and aluminum on absorption, metabolism, and mechanism of renal elimination of pefloxacin in humans.

The effects of an antacid containing magnesium and aluminum hydroxide on the pharmacokinetics of pefloxacin in 10 healthy volunteers were investigated. In a randomized crossover design, each subject received an oral dose of 400 mg of pefloxacin either with or without multiple doses of the antacid. The concentrations of pefloxacin and its metabolites in plasma and urine were determined by high-performance liquid chromatography assays. We found that coadministration of magnesium and aluminum hydroxide caused a decrease of levels of pefloxacin in plasma and urine. The area under the plasma concentration-time curve decreased significantly (P < 0.001), suggesting impaired absorption of pefloxacin from the gastrointestinal tract. The relative bioavailability of pefloxacin after the antacid treatment was 44.4% +/- 23.8%, compared with that after a single administration. The underlying mechanism of this drug interaction is the formation of chelate complexes and probably also physical adsorption to the aluminum hydroxide gel. The metabolism of pefloxacin was not altered by the antacid treatment. Renal clearance was found to depend on urinary pH. Terminal half-life was significantly shorter after the antacid treatment, probably because of an increase in nonrenal clearance. In conclusion, pefloxacin should be given at least 2 h before the antacid to ensure sufficient therapeutic efficacy of the quinolone.

[Clinico-pharmacologic studies on pefloxacin]. / Klinikofarmakológiai vizsgálatok Péflacine-nal.

The impact of liver impairment, renal insufficiency and age-related changes on the pharmacokinetics of pefloxacin was studied in 55 patients. The elderly patients were stratified into three age groups (61-70, 71-80 and above 81 years). The patients suffering from various infections were treated with oral or intravenous pefloxacin in a dose of 400 mg bid. Blood samples were withdrawn on the first and seventh day of therapy. The pharmacokinetics of pefloxacin was characterized by marked interindividual differences that became even more pronounced during multiple dosing. The elimination rate of pefloxacin during therapy slowed down, presumably due to its decreased metabolism. In elderly patients, the rate of cumulation is greater than in the young ones, but no significant differences could be detected among the elderly age-groups. Pefloxacin elimination also decreased in renal and hepatic impairment. There was no correlation between serum concentrations of pefloxacin and the development of adverse effects. In elderly subjects and in patients with renal or hepatic impairment, dose reduction might be considered. In mild or moderate infections or in urinary tract infections smaller doses of pefloxacin also could assure good therapeutic results. However, in severe infections especially caused by less susceptible pathogens, routine dose reduction is not recommended because of the significant interindividual differences in serum concentrations of pefloxacin.

[Effect of ketoprofen on the pharmacokinetics of two fluoroquinolones in males]. / Influence du kétoprofène sur la pharmacocinétique de deux fluoroquinolones chez l'homme.

The influence of a non steroidal antiinflammatory drug (NSAID), ketoprofen, on the pharmacokinetics of two fluoroquinolone derivatives, pefloxacin (P) and ofloxacin (O), was studied in ten healthy adult male volunteers. The subjects were given orally for three days the quinolone alone (P: 400 mg q 12 h and O: 200 mg q 12 h), with at least a one week interval between the two quinolone studies. On day 4, the first kinetic study of pefloxacin and ofloxacin was performed. During the three following days, the quinolone was administered in association with ketoprofen (100 mg daily). Another pharmacokinetic study of P and O was performed on day 8 and the kinetic data obtained were compared to those found on day 4. During the two kinetic studies (D4 and D8), blood samples were taken at times 0, 1, 2, 3, 4, 6, 8, 10, 12 et 24 h and urine was collected during the time-periods 0-4 h, 4-8 h, 8-12 h and 12 24 h. Plasma and urine concentrations of the active P and O drug were measured by microbiological assay. Ketoprofen administered for three days with the fluoroquinolone derivative induced no statistical modification in the kinetic parameters of both P and O: peak plasma levels, time to peak level, areas under the curve, apparent volume of distribution, total and renal clearances.

Effects of ketoprofen (NSAID) on the pharmacokinetics of pefloxacin and ofloxacin in healthy volunteers.

The influence of ketoprofen (K), a non steroidal antiinflammatory drug (NSAID) on the pharmacokinetics of two fluoroquinolone derivatives: ofloxacin (O) and pefloxacin (P) was studied in ten healthy adult male volunteers. All subjects orally received every 12 h the fluoroquinolone derivative (either O or P) for three days and the combination of the quinolone and ketoprofen (once a day) during the three following days. Two pharmacokinetic studies were performed for each quinolone, on days four and eight of the treatment. Blood samples were taken at times 0, 1, 2, 3, 4, 6, 8, 10, 12 and 24 h after dosing. Urine was collected during 4 time-periods: 0-4 h, 4-8 h, 8-12 h and 12-24 h. Plasma and urine concentrations of the active drug of O and P were measured by microbiological assay. Ketoprofen did not significantly modify the pharmacokinetic parameters of the two fluoroquinolones studied in terms of peak plasma levels, time to peak, area under the curve, elimination half-life, volume of distribution and total and renal clearances.

Pharmacokinetics of quinolones in renal insufficiency.

The pharmacokinetics of the new fluoroquinolone derivatives have been extensively studied in patients with various degrees of chronic renal insufficiency during the last few years. Their kinetic profiles depend on the elimination pathways and on the degree of metabolic transformation. Renal insufficiency does not significantly modify pefloxacin kinetics. For the other new quinolones, a decrease in glomerular filtration rate below 20-30 ml/min induces an increase in terminal half-life and a decrease in plasma and renal clearance, related to the degree of renal impairment. These drugs are poorly removed by haemodialysis. Dosage adjustments are required, particularly in severe renal failure and for the drugs almost exclusively excreted, in unchanged form, via the renal route.

[Antibacterial activity of pefloxacin in the urine during the 7 days following a single 800 mg oral dose]. / Activité antibactérienne de la péfloxacine dans l'urine durant sept jours après prise orale unique de 800 mg.

Antibacterial activity of pefloxacin was studied in the urine after a single 800 mg oral dose in ten healthy female volunteers. Urine was collected in 9 periods: 0-6 h, 6-12 h, 12-24 h, 24-28 h, 48-72 h, 72-96 h, 96-120 h, 120-144 h, 144-168 h. Pefloxacin concentrations were assayed in all samples by a microbiological method and by HPLC. Urine antibacterial activity was determined towards five bacterial strains isolated in urine: 2 E. Coli strains, one sensitive and the other resistant to nalidixic acid (Nal-A), 1 Klebsiella pneumoniae resistant to nalidixic acid (Nal-B), 1 Staphylococcus saprophyticus and 1 Streptococcus faecalis; MIC's of pefloxacin against these strains were respectively 0.015, 0.25, 1, 0.50 and 2 micrograms/ml. Pefloxacin mean concentrations as determined by the microbiological method were 91.8 +/- 11.9, 71.7 +/- 7, 44.5 +/- 4.3, 24.4 +/- 4 and 5.4 +/- 0.8 micrograms/ml in the five first urine samples; low levels were present in the urine until the 7th day in 8 volunteers. HPLC results completed the already known data concerning pefloxacin elimination and metabolism; unchanged pefloxacin was excreted at the highest concentration during the 6 first hours; then demethylpefloxacin was eliminated at higher levels than pefloxacin with a ratio of 2/1 after the 24th hour. These two compounds were detectable in the urine during 5 to 7 days; oxodemethylpefloxacin and N-oxyde-pefloxacin were present in lower amounts and during a shorter period.(ABSTRACT TRUNCATED AT 250 WORDS)

N-oxidation, N-demethylation, and excretion of pefloxacin by the turtle Pseudemys scripta elegans.

Pefloxacin is minimally absorbed by the gastrointestinal tract of the turtle Pseudemys scripta elegans and then N-oxidised and N-demethylated. Pefloxacin is excreted within one hour after being given orally to the turtles.