A specific and rapid HPLC assay for the determination of cefroxadine in human plasma and its application to pharmacokinetic study in Korean.

A specific and rapid high performance liquid chromatographic (HPLC) method with UV detection (254 nm) was developed for the determination of cefroxadine in human plasma. The sample extraction was performed by a simple procedure, vortexing and centrifugation of sample following addition of 60% trichloroacetic acid. Cephalexin was used as an internal standard (I.S.). The HPLC analysis was carried out on a Capcell Pak C18 analytical column with a mobile phase of 50 mM ammonium formate buffer/pH 3.5 and acetonitrile (90:10, v/v). No interference was observed near the peaks of cefroxadine and I.S. The calibration curve was linear over the range of 0.5-40 microg/mL and the lower limit of quantification (LLOQ) was 0.5 microg/mL. The method was validated with excellent sensitivity, accuracy, precision and stability. This assay was successfully applied to determine the pharmacokinetic parameters of cefroxadine in Korean healthy volunteers after an oral administration of two 250 mg cefroxadine capsules. As a result, the plasma half-life was 1.00+/-0.26 h and the mean AUC(0-6 h) was 46.25+/-6.41microgh/mL. The maximum plasma concentration (C(max)) of 17.62+/-4.87 microg/mL reached 1.44+/-0.39 h after administration.

Synthesis and antibacterial activity of cephradine metal complexes : part II complexes with cobalt, copper, zinc and cadmium.

Cephradine, the first generation cephalosporin, is active against a wide range of Gram-positive and Gram-negative bacteria including penicillinase-producing Staphylococci. Since the presence of complexing ligand may affect the bioavailability of a metal in the blood or tissues, therefore, in order to study the probable interaction of cephradine with essential and trace elements present in human body, cephradine has been reacted with cobalt, copper, zinc and cadmium metal halides in L:M ratio of 2:1 in methanol and the products recrystallized from suitable solvents to pure crystals of consistent melting points. Infrared and ultraviolet studies of these complexes were carried out and compared with ligand. Magnetic susceptibility studies of these complexes were also carried out showing their paramagnetic behavior. From the infra red studies and elemental analysis of the complexes, it has been shown that the drug molecule serves as a bidentate ligand coordinating through both its carboxylate at C-3 and beta-lactam nitrogen and the metal having a square planar or octahedral geometry. To evaluate the changes in microbiological activity of cephradine after complexation, antibacterial studies were carried out by observing the changes in MIC (minimum inhibitory concentration) of the complexes and compared with the parent drug by measuring the zone of inhibition of complexes and compared with the parent cephalosporin against both Gram-positive and Gram-negative organisms. For MIC observation, serial dilution method was employed and zone series were determined by disk diffusion method. Our investigations reveal that formation of complexes results in decrease in antibacterial activity of cephradine and MIC values are increased.

pH-dependent inhibitory effects of angiotensin-converting enzyme inhibitors on cefroxadine uptake by rabbit small intestinal brush-border membrane vesicles and their relationship with hydrophobicity and the ratio of zwitterionic species.

The inhibitory effects of five angiotensin-converting enzyme (ACE) inhibitors on the uptake of an aminocephalosporin antibiotic, cefroxadine, by rabbit small intestinal brush-border membrane vesicles were examined in the presence of an inward H+ gradient. Dixon plot analysis showed that all these ACE inhibitors inhibited the uptake of cefroxadine, which is transported by a H+/oligopeptide transporter in the membrane, in the order of enalapril

Inhibitory effects of angiotensin-converting enzyme inhibitor on cefroxadine uptake by rabbit small intestinal brush border membrane vesicles.

Effects of angiotensin-converting enzyme (ACE) inhibitors, captopril, enalapril maleate and quinapril, on the uptake of aminocephalosporin antibiotic, cefroxadine, by rabbit small intestinal brush border membrane vesicles were examined. These ACE inhibitors significantly inhibited the uptake of cefroxadine, which is transported by H+/dipeptide transporter in the membrane, in the order of captopril < enalapril < quinapril in the presence of an inward H+ gradient. Inhibitory effect of quinapril was more marked than that of aminocephalosporin cephradine, while in the absence of an inward H+ gradient inhibition by these ACE inhibitors was much less. Dixon plot analysis showed that the inhibition by enalapril and quinapril in the presence of an inward H+ gradient occurred in a competitive manner and estimated inhibition constants of these two drugs to be 5.3 mM and 0.46 mM, respectively. These results suggested the strong affinity of these ACE inhibitors, especially quinapril, on the H+/dipeptide transporter.

Characteristics of uptake of cefroxadine by rabbit small intestinal brush border membrane vesicles.

Characteristics of transport of an oral aminocephalosporin, cefroxadine, in rabbit small intestinal brush border membrane vesicles were examined. Uptake rate of cefroxadine was saturable in the presence of an inward H+ gradient, and kinetic parameters were similar to those of cephradine. However, the uptake rate was almost linear with the concentration in the absence of an inward H+ gradient up to 5 mM. Overshoot phenomenon was observed in the presence of an inward H+ gradient at 37 degrees C, but it disappeared with decrease of temperature. The Arrhenius plot of uptake rate constant showed a break point at approximately 30 degrees C. Cefroxadine uptake was optimum in the vicinity of pH 5.5 at 37 degrees C, but the dependence on extravesicular pH disappeared at 15 degrees C. The uptake of cefroxadine in the presence of an inward H+ gradient was markedly inhibited by other aminocephalosporins such as cephalexin, but the inhibition was only slight in the absence of an inward H+ gradient. Alkyl alcohols such as n-hexyl alcohol also inhibited H(+)-coupled uptake of cefroxadine at the concentration range at which the alcohols increased the membrane fluidity, and overshoot phenomenon diminished, suggesting that H(+)-coupled transport of cefroxadine is sensitive to the alcohol-induced increase in membrane fluidity. On the other hand, the alcohols rather stimulated its uptake in the absence of an H+ gradient.

Isolation and structural elucidation of an impurity of cefradine.

An impurity of unknown identity was isolated from commercial cefradine by liquid chromatography on poly (styrene-divinylbenzene) with HOAc (0.01 M)-CH3CN (94:6, v/v) as the mobile phase. The structure was elucidated as 4',5'-dihydrocefradine using nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS). The structure was confirmed by comparison with the chromatographic retention characteristics and photodiode-array detected ultraviolet spectrum of the synthetic compound and with its infrared, NMR and MS spectra. The presence of 4',5'-dihydrocefradine in cefradine has not been described previously.

Comparison of continuous, constant rate enteral tube feeding in supine patients to bolus food intake in ambulatory, healthy subjects regarding bioavailability of perorally administered cefroxadine.

Stabilized, bedridden, inactive trauma patients on enteral nutrition via continuous, constant rate tube feeding (2 different formulas) were given a single dose of cefroxadine p.o. There were no differences in the pharmacokinetic parameters between the groups on different enteral nutrition. These patients were compared to cefroxadine absorption in ambulatory healthy subjects after a standardized meal (bolus-fed). The mean residence time was significantly longer in the patients, and the extent of absorption was slightly reduced with one enteral nutrition formulation and significantly reduced with the other. The other pharmacokinetic parameters were not significantly different. The difference is believed to be caused by reduction in splanchnic blood flow in the immobilized patients, weakening of migrating motor complex due to tube feeding and the lower temperature (4 degrees C) of enteral nutrition.

Peroral absorption of cefroxadine in patients within the first day after severe trauma: comparison to cefroxadine pharmacokinetics in fasted, healthy volunteers.

Peroral absorption of cefroxadine given to 7 24-h fasted trauma patients by nasogastric tube within the first day of admission was compared to that obtained in fasted healthy volunteers. The trauma patients exhibited significantly lower Cmax and reduced AUC. Even though rate and extent of bioavailability cannot be determined from these two different population groups since the total clearance must be assumed to be different in patients and healthy subjects, a reduced bioavailability is assumed based on pathophysiologic reflections.

Effects of cefroxadine on L-leucine absorption in rat jejunum.

The effect of cefroxadine, an aminocephalosporin (beta lactam antibiotic) on rat intestinal L-leucine transport has been studied. Cefroxadine inhibited the L-leucine uptake by the intestinal mucosa in a dose-dependent fashion. In vivo studies showed that cefroxadine reduced L-leucine absorption. This effect was irreversible. Only the active transport component of the absorption was inhibited. Oxygen consumption of the mucosa was reduced by cefroxadine which inhibited the activity of the basolateral (Na(+)-K+) ATPase also.

Pharmacokinetics of cefroxadine after infusion to healthy volunteers.

The pharmacokinetics of cefroxadine in healthy human volunteers was studied in plasma and urine, after an infusion administration of 1 g of this drug for 0.5 h. Blood and urine samples were microbiologically quantified by diffusion on solid gelose using Bacillus Subtilis ATCC 6633 as the test organism. Plasma and urine profiles were fitted to a reduced two-compartment model not having inactivating biotransformation as a route of elimination. The parameters of distribution for this model show a rapid disposition (t1/2 alpha = 0.28 h) and an average volume of the central compartment of 0.15 +/- 0.04 l/kg (range 0.20-0.09). The dominant terminal half-life (beta-phase) was 1.17 +/- 0.26 h (range 0.90-1.67). The total body volume 0.41 +/- 0.09 l/kg (range 0.30-0.52) indicates that there is no diffusion of the antibiotic into intracellular fluids of poorly perfused tissues due to its high elimination rate.

In-vitro evaluation of a new oral cephalosporin, cefroxadine (CGP 9000).

The in vitro activity of cefroxadine was studied and found to be at least comparable to that previously reported for cefalexin and cefradine. The activity of cefroxadine was superior to that of amoxicillin against tested isolates. Time-killing studies showed that the addition of 4 X minimum inhibitory concentration (MIC) of cefroxadine to growing cultures reduced viable counts by 4 log units within a 3 h incubation. A diffusion test with a 30 microgram cefroxadine disk produced acceptable interpretive results with tentative zone size breakpoints of less than or equal to 14 mm for resistance and greater than or equal to 17 mm for susceptibility.

Cefroxadine in the treatment of children affected by respiratory and ENT diseases. A multicentre study involving 1072 in-patients.

In this multicentre trial, 1072 hospitalized children, 573 boys and 499 girls (847 of whom were aged less than 6 years), affected by respiratory tract (376 patients) or ENT (696 patients) infections were treated for 10 days with cefroxadine per os, at an average dose of 650 mg/day (325 mg every 12 h corresponding to 25 mg/kg b.w.). Most patients (1047; 97.7%) completed the trial, while 25 patients were withdrawn from the study (20 patients for viral diseases and 5 for side-effects). Of the patients affected by respiratory tract infections, 361 completed the trial and 342 of them (94.7%) were cured in 6.0 days on average. Of the patients affected by ENT infections, 686 completed the trial and 649 of them (94.6%) were also cured in an average of 6.0 days. In the two groups the signs and symptoms of the disease significantly (p less than 0.001) decreased by the end of the study. Some patients (80; 7.6%) complained of side-effects, mainly gastric discomfort (4.9%), skin rash (2.2%) and glossitis (0.5%). In conclusion, cefroxadine exerts a satisfactory antibacterial action with only a few days of treatment, and it appears to be very well tolerated.

Microbore liquid chromatographic determination of cadralazine and cephalexin in plasma with large-volume injection.

The application of microbore systems (15 cm X 1 mm I.D. columns filled with Nucleosil C18, 5 microns particle size) to the determination of cephalexin and cadralazine in plasma was investigated. Factors such as mobile phase flow-rate, detector flow-cell volume and injection volume were examined with regard to the needs of routine drug analysis. Mobile phase flow-rates of 50-60 microliters/min were used. A flow cell with an optical path length of 6 mm and an intermediary volume (2.4 microliters) was selected for UV detection in order to obtain sufficient sensitivity. Large volumes of non-eluting solvent containing the drug were injected on the column. The addition of an ion-pairing reagent to samples containing cephalexin and cefroxadin prior to the injection was found to improve the chromatographic performance. The blood sample size required for analysis with microbore columns was smaller than that with conventional columns. The analysis time was similar and the limit of quantitation was also similar, provided that large sample volumes were injected on the microbore column.

Correlation between plasma and tonsillar levels of cefroxadine.

Serum and tonsillary tissue levels of cefroxadine, a new broad-spectrum cephalosporin, proving to be effective in several infections, particularly in the ENT ones, were measured in patients scheduled for tonsillectomy. Twenty patients (12 males, 8 females) aged between 11 and 25 years (mean 18.0 years) were given cefroxadine for 2 days (500 mg every 12 h), and on the 3rd day 500 mg of the drug was given before surgical operation. Tonsillar tissues were taken 2 h after dosing and blood samples before, 1, 2, 4 and 6 h after the drug administration in 8 out of 20 enrolled patients. Cefroxadine concentrations were measured according to microbiological methods. Cefroxadine tonsillary levels were 1.13 +/- 1.73 micrograms/g, approaching the MIC for sensitive bacteria. The time course of plasma levels is superimposable to previous studies. These findings suggest a rapid penetration of cefroxadine in tonsillar tissue and seem to confirm the clinical efficacy of the drug in ENT infections.

[A clinical study on cefroxadine in the treatment and recurrence of acute uncomplicated cystitis].

Cefroxadine (CXD) was administered to patients with acute uncomplicated cystitis (AUC) in a dose of 250 mg t.i.d. for 3-7 days. The patients were divided into 2 groups (less than 70 and greater than or equal to 70 years old) and clinical efficacy and incidents of recurrence were assessed. 1. Out of 83 patients treated, clinical efficacy was evaluated in 62 patients including 10 elder patients on the 3rd day and in 47 patients including 9 elder patients on the 7th day. In both groups clinical efficacy rates were 100% on the 3rd and 7th day. 2. Among 24 patients including 7 elder patients, who showed excellent response on the 7th day, recurrence was examined on the 14th day. The recurrence rate was 0% by the criteria proposed by the UTI committee in Japan. However, two patients (under 70 years of age) among them were considered as positive for recurrence by doctors in charge. Consequently, in both aged groups CXD showed excellent results in the treatment of AUC.

Determination of the thermodynamic ionization constants of cefroxadine.

The values of the thermodynamic ionization constants of the carboxylic (pK = 3.30 +/- 0.02) and amine (pK = 7.00 +/- 0.06) groups of cefroxadine were determined at 35.0 degrees C using potentiometric data. The apparent ionization constants of these groups were also determined at 35.0 degrees C, and at different values of ionic strength.