Antibacterial effects of cefroxadine, cephalexin and cephradine in a new in vitro pharmacokinetic model

A pharmacokinetic model has been developed, by means of which all possible time courses of the concentrations of antibiotics in the plasma of treated individuals can be exactly simulated in vitro without diluting the test organism and affecting the growth curves. Equieffective concentrations in the system corresponded to the plasma concentrations in man produced by cefroxadine in a single oral dose of 250 mg and cephalexin and cephradine in a single oral dose of 500 mg.

Determination of cefsulodin, cefotiam, cephalexin, cefotaxime, desacetyl-cefotaxime, cefuroxime and cefroxadin in plasma and urine by high-performance liquid chromatography

Closely related methods for the determination of several cephalosporins in plasma and urine are described. Deproteinized plasma or diluted urine is directly injected on a RP-8 or RP-18 bonded-material column. Chromatography is performed either in the reversed-phase or the ion-pair mode. The limits of sensitivity range from 0.4 to 2 mumol of cephalosporins per liter of plasma, and from 20 to 100 mumol per liter of urine. The sensitivity may be improved two to five times by using precolumn loading, direct sample clean-up and automatic injection. The stability of the cephalosporins in plasma, urine and water and the reproducibility and accuracy of the methods are reported.

The pharmacokinetics of cefadroxil associated with probenecid

The effects of probenecid on the pharmacokinetic parameters of cefadroxil administered in a single dose of 500 mg are studied. The serum and urine levels of the antibiotic were determined by a microbiologic plate diffusion method. The antibiotic follows a single-compartment model. The half-life of cefadroxil in serum has an average value of 1.13 h, rising to 1.63 h when the antibiotic is associated with probenecid. The apparent distribution volume remains unmodified with a value close to 23 liters. The lag time is 0.25 h in the absence of probenecid, rising to 1.029 h in the presence of the uricosuric agent.

[The comparison of blood levels between peripheral vein and tooth extraction wound after the oral administration of antibiotics (author's transl)]

The oral administration of 300 mg of clindamycin was undertaken on 23 patients, of 500 mg of cefadroxil on 11 patients and of 250 mg of talampicillin on 12 patients, and then tooth extraction was performed under local anesthesia. Blood samples were taken from the extraction wound and the peripheral vein at the same time and assayed by the bioassay method. The blood levels of clindamycin and cefadroxil indicated a similar pattern between the extraction wound and the peripheral vein, but the blood level of talampicillin reached peek level rapider than clindamycin and cefadroxil. The blood levels of the extraction wound were 60 - 80% as compared with the venous blood levels with each antimicrobial agent.

[Clinical results of cefadroxil in children and pharmacokinetics of the drug (author's transl)]

Cefadroxil was administered orally at a daily dose of 30-40 mg/kg to 8 cases of the infection of upper respiratory tract mainly due to beta-hemolytic Streptococcus, and efficacy was obtained in 7 cases, this rate being considered to be satisfactory, though the cases were too few to reach a conclusion. As to pathogens of bacterial infection of upper respiratory tract, beta-hemolytic Streptococcus and Staphylococcus aureus were encountered especially frequently, and in view of antibacterial activity against these 2 bacteria, our results could be approved. Further investigations should be performed carefully, however, to determine if cefadroxil may be a drug of first choice in the treatment of severe bacterial pneumonia and pyothorax. No side effects were observed throughout our treatment, though digestive tract disorders, especially diarrhea, are most frequent in literatures. As to pharmacokinetical characteristic of cefadroxil, almost the same results were obtained to other reports, though our data are insufficient as our experience was limited in only 1 case. Serum levels were determined after 35.7 mg/kg of cefadroxil were administered once orally, and a peak of about 38 mcg/ml appeared 2 hours later, and a high level of about 30 mcg/ml was maintained at 5 hours, though an oral dose was high. Efficacy for large area of bacterial infections may be expected from these serum levels. From urine collected simultaneously, about 74% of cefadroxil was recovered within more than 4 hours. This showed that cefadroxil was well absorbed from digestive tract, and a major part was excreted rapidly through kidney. From the results of our experiment, characteristics of cefadroxil may be summarized as follows. Cefadroxil is absorbed well after oral administration, antibacterial action is fully expected from serum level, a major part is excreted through kidney, and clearance is good. Cefadroxil will be recommended especially for bacterial infections of upper respiratory tract due to beta-hemolytic Streptococcus and Staphylococcus aureus.

Influence of dose on the pharmacokinetics of cefadroxil

The pharmacokinetics of Cefadroxil have been studied in a crossover study involving 20 experiments in four healthy volunteers (19--24 years), after oral administration of five individual doses of 250, 500, 750, 1000 and 1500 mg of the antibiotic in capsules to each person. Plasma and urine concentrations of the antibiotic were determined microbiologically by a plate diffusion method. The antibiotic followed an open, single-compartment kinetic model. The plasma half-life was not significantly influenced by dose; the average was 1.438 +/- 0.220 h. The percentage of the antibiotic excreted in urine, too, was not significantly affected by the dose, being close to 80% of the quantity originally administered within 24 h. The values of Cmax and (AUC) increased linearly with the administered dose.

[Pharmacokinetics of cefadroxil in rats: comparison of fasting and non-fasting (author's transl)]

A single dose 50 mg/kg of cefadroxil was administered orally to rats in fasting and non-fasting. In both fasting and non-fasting, the serum levels of cefadroxil were higher than those of cephalexin. In fasting, the biological half-life (T 1/2) of cefadroxil was longer than that of cephalexin. This indicates its prolonged durable action. Ingestion of cefadroxil with food affected the serum level less than that of cephalexin with food, and the serum levels of cefadroxil in non-fasting were same as those of cephalexin in fasting.

[Microbiological assay method of cefadroxil in biological specimens (author's transl)]

A microbiological method for quantitative determination of cefadroxil in biological specimens is described. This method is essentially a cylinder-plate or a paper-disc method using Micrococcus luteus ATCC 9341 as the test organism grown in the tryptosoya broth added with 1.5% agar. Cefadroxil standard calibration curves are prepared in pooled human serum, moni-trol I or consera for the determination of serum level of human, and 0.1 M phosphate buffer (pH 6.0) to determine urine level. Cefadroxil in human serum and urine specimens can be measured by cylinder-plate method as low as 0.16 approximately 0.31 micrograms/ml and 0.08 approximately 0.16 micrograms/ml, respectively. Further, any active metabolites of cefadroxil were not detected on human and rat urine specimens by bioautography.

Serum levels and urinary excretion in humans of BL-S 578 (cefadroxil), a new semisynthetic cephalosporin

Single doses of 250 and 500 mg of BL-S 578 (cefadroxil), a new semisynthetic cephalosporin, were orally administered to 13 normal, healthy volunteers and serum levels determined at timed intervals for 7 h. Peak concentration was obtained at 1 1/2 h after administration of 250 mg (8.981 micrograms/ml) or 500 mg (17.861 micrograms/ml). Urniary excretion levels within 24 h after ingestion of single doses of 250 and 500 mg of cefadroxil were 89.92 and 86.34%, respectively.

Use of the serum bactericidal titer to assess the adequacy of oral antibiotic therapy in the treatment of acute hematogenous osteomyelitis

Serum bactericidal titers against Staphylococcus aureus were measured in 63 children who were receiving mafcillin or methicillin intravenously, or dicloxacillin, penicillin, or cephalexin orally. The SBTs obtained following unit does of 25 mg/kg of dicloxacillin, 35 mg/kg of penicillin, or 25 mg/kg of cephalexin with probenecid were comparable to those seen following intravenous doses of 40 mg/kg nafcillin or methicillin. Twenty-two children with acute hematogenous osteomyelitis proven or presumed to be due to S. aureus were treated intravenously until point tenderness and fever had resolved, and then with oral therapy. The mean duration of intravenous therapy was 14 days. Oral doses were adjusted so that a peak SBT of greater than or equal to 1:16 and a trough SBT of greater than or equal to 1:2 were obtained in most children. No recurrences occurred. The SBT proved to be a practical means of assessing the adequacy of oral therapy in children with infections due to S. aureus.

Bactericidal activity of cefadroxil, cephalexin, and cephradine in an in vitro pharmacokinetic model

Cefadroxil (Duricef, Mead Johnson and Company), resembles cephalexin and cephradine in spectrum of antibacterial activity but differs in human pharmacokinetic properties. Whether the latter are likely to affect activity in vivo was assessed by determining bactericidal activity against clinical isolates under conditions simulating the variation of drug concentration in the blood stream after an oral dose of 500 mg to adults. In this kinetic model, cefadroxil was more active than cephalexin or cephradine against Staphylococcus aureus, Streptococcus pneumoniae, Klebsiella pneumoniae, Proteus mirabilis, Haemophilus influenzae and one of two strains of Escherichia coli. The other strain of E. coli was virtually unaffected by the cephalosporins. S. pyogenes was equally susceptible to all three cephalosporins. Analysis of the results suggest that the pharmocokinetic properties of an antibiotic affect its activity in the blood stream, provided the susceptibility of the infecting organism is concentration-dependent within the range of drug concentration occurring in serum.

Concentrations of cephalexin in mandibular alveolar bone, blood, and oral fluids

Results from this study of 16 patients who underwent extractions and alveoloplasty indicate that cephalexin effectively penetrates alveolar bone. After cephalexin had been administered, 500 mg four times a day for 48 hours, the average concentration in bone exceeded the average minimal inhibitory concentration of six organisms commonly encountered in infections and bacteremias of dental origin. These data and the current knowledge of cephalexin suggest that cephalosporins may have a unique use in dental infections or potentially harmful bacteremias caused by susceptible organisms.

Comparative pharmacokinetics of cephalexin, cefaclor, cefadroxil, and CGP 9000

In a randomized crossover study, the pharmacokinetics of three new cephalosporin antibiotics, cefaclor, cefadroxil, and CGP 9000, in comparison to cephalexin, were determined after oral administration, by capsules, of 1,000 mg on an empty stomach in 12 normal subjects. Serum concentrations were measured during a period of 8 h, and urine recovery was measured during 24 h. The significant parameters of bioavailability of an orally administered substance were determined. The maximal serum concentrations (y(max)) for cephalexin, cefaclor, cefadroxil, and CGP 9000 (in milligrams per liter) were: 38.8 +/- 8.1; 34.6 +/- 7.8; 33.0 +/- 5.4; and 23.3 +/- 7.3, respectively. The areas under the curve (in hours x milligrams per liter) were: 93.0 +/- 14.8; 74.5 +/- 9.9; 70.1 +/- 9.0; and 108.5 +/- 18.4, respectively. In a further crossover study with six subjects, 1,000 mg of cephalexin and of cefadroxil were given during a standard breakfast. The y(max) of cephalexin decreased to 23.1 +/- 6.6 mg/liter, in contrast to cefadroxil, with an unchanged y(max) of 32.7 +/- 3.4 mg/liter.

[Aqueous-and serum levels of cephalexin and penicillin V after oral application in man (author's transl)]

This clinical study implies orally administered cephalexin and penicillin V as agents with effective aqueous homor penetration in noninfected human eyes. Aqueous humor concentration of cephalexin increases up to 15% of the serum level 2 h after application. Administration of 1 g or 2 g cephalexin revealed no significant difference in aqueous humor concentration. So penetration of blood-aqueous-humor barrier can be regarded as a saturation process. Individual results of 92 cephalexin determinations are variant and not related to body weight or age of the patients.

Evaluation of an oral prolonged-release antibiotic formulation

The antibiotic cephalexin was formulated as an oral prolonged-release tablet and evaluated by in vitro dissolution testing as well as in vivo in 10 human subjects. Comparisons were made of the time course of the blood levels among the prolonged-release formulation, the commercially available capsule, and intravenous administration. Even though lower peak blood levels were attained in the prolonged-release tablet, absorption continued for at least 6 hr. Comparison with in vitro dissolution data showed that absorption was dissolution rate limited. Bioavailability comparisons showed that the prolonged-release formulation was completely available, as was the commercial oral capsule.

[Study of S-6437 in pediatrics regarding clinical efficacy, blood levels and urinary excretion (author's transl)]

S-6437 was orally given to 29 patients of 3 months to 12 years and 6 months of age who had respiratory or urinary tract infections. The daily dose used was 25 to 60 mg/kg divided in two doses. The following is the results of this study: 1. With 25 approximately 60 mg/kg/day, satisfactory results were obtained for upper respiratory tract infections. In lower respiratory tract infections, however, the effectiveness seemed not to be so good as that in upper respiratory tract infections. 2. Side effects such as diarrhea, loose stool, abdominal pain and eruption were observed but they were temporary. Therefore, the administration of S-6437 was not discontinued due to such side effects. 3. S-6437 was acceptable to elder children but some of children of 2 approximately 4 years of age disliked this preparation because it was not smooth in their mouths. Therefore, the preparation of S-6437 should be further improved. 4. Since it has been recognized that blood levels of cephalexin following the administration of S-6437 last for a longer period of time than regular cephalexin, S-6437 is considered to be a useful preparation. 5. B.I.D. and T.I.D. regimens of S-6437 will give clinical satisfaction to children over 6 years and ones under 6 years, respectively.

Fluorimetric assay of cephradine, cephalexin and cephaloglycin

1 A simple, rapid and reproducible fluorimetric assay for cephradine, cephalexin and cephaloglycin is described. 2 The method involves addition of formaldehyde which catalyses the formation of fluorescent derivatives. 3 The structural similarities between the side chains of these antibiotics and their identical excitation and emission spectra suggest that they may be forming similar fluorescent derivatives.