Penetration of cefpiramide and cefazolin into peritoneal capsular fluid in rabbits

Aerosol inhalation delivery of cefazolin in mice: Pharmacokinetic measurements and antibacterial effect

Aerosol inhalation delivery of cefazolin, a broad-spectrum first-generation cephalosporin antibiotic, was investigated. Inhalation system based on ultrasonic nebulizer was developed for the generation of dry cefazolin aerosol within mean particle diameter range 0.5-3.0 μm and mass concentration 0.01-3 μg/cm³. Pharmacokinetic measurements were carried out for the aerosolized form of cefazolin delivered in mice using nose-only chamber. Cefazolin concentrations in blood serum and in the lungs of mice were measured as a function of time by means of high performance liquid chromatography. Body-delivered dose depending on particle size, concentration and inhalation time as well as other pharmacokinetic parameters were determined. The antibacterial effect of aerosolized cefazolin was assessed through the aerosol inhalation treatment of mice infected with Klebsiella pneumoniae. Survival rate for infected mice after the treatment with cefazolin aerosol demonstrated high antibacterial efficiency of the inhalation delivery of cefazolin in comparison with intraperitoneal delivery.

Determination of cephazolin, ceftazidime, and ceftriaxone distribution in nucleus pulposus

BACKGROUND

The intervertebral disc is the largest avascular structure in the adult body and minimal blood flow through capillary beds only supplying the outer regions of the disc, which relies on the passive diffusion as a major factor for nutrition and uptake of molecules, including antibiotics. This study is to detect the serum and nucleus pulposus (NP) levels of cephazolin, ceftazidime, and ceftriaxone and to assess this antibiotic permeability into the intervertebral disc.

METHODS

Forty-five consecutive patients undergoing lumbar interbody fusion surgery were divided into three groups to participate in the study. Approximately 30 min before the procedures, a bolus dose 2 g antibiotic of cephazolin, ceftazidime, and ceftriaxone was administered intravenously. The NP tissue and serum sample levels of antibiotic were assayed by high performance liquid chromatography.

RESULTS

Three cases failed in the ceftriaxone group because the NP tissue contaminates the blood. Average time between antibiotic injection and tissue/blood collection was 41 min (range 27-57 min). The antibiotic concentration level of cephazolin, ceftazidime, and ceftriaxone was 144.26 ± 29.15, 127.19 ± 30.22, and 227.81 ± 51.48 μg/ml in serum and 2.33 ± 0.45, 3.74 ± 1.91, and 2.23 ± 1.86 μg/g in NP, respectively. The antibiotic penetration in to NP of cephazolin was 1.67 ± 0.44, 2.99 ± 1.99 of ceftazidime, and 1.08 ± 1.44 of ceftriaxone.

CONCLUSIONS

The antibiotics of cephazolin, ceftazidime, and ceftriaxone had concentration in the NP tissue, which was higher than the stated MIC. Ceftazidime had highest penetration in to NP tissue, and ceftriaxone had the lowest penetration in to NP tissue.

Protein binding of cefazolin is saturable in vivo both between and within patients

AIMS

The aims of the study were a) to determine if there is evidence of saturable protein binding of cefazolin in plasma across the range of concentrations achieved clinically (between patient variability) and b) to investigate whether saturable protein binding is also evident from trough and peak concentrations in the same patient (within patient variability).

METHODS

Unbound and total plasma concentrations were measured in patients who were treated with cefazolin intravenously by continuous infusion or intermittent injection. In study (i) single random samples were taken from one series of patients. In study (ii) paired samples (troughs and peaks) were taken from a second series of patients.

RESULTS

Thirty-one patients were included in study (i). Linear regression analysis of the percentage unbound vs. unbound plasma concentrations revealed a slope significantly different from zero, suggesting saturable protein binding. Mean values for percentage unbound ranged from 9% at low concentrations (8.5 mg l(-1)) to 51% at high concentrations (140 mg l(-1)). Twelve patients were investigated in study (ii). Values for protein binding ranged from 85% at low concentrations (2.7 mg l(-1)) to 52% at high concentrations (200.3 mg l(-1)). The percentage unbound was significantly higher (P < 0.0001) at high (peak) concentrations than at lower (trough) concentrations, confirming saturable protein binding.

CONCLUSIONS

The protein binding of cefazolin is saturable in vivo in humans, both between and within patients.

In vivo animal models: quantitative models used for identifying antibacterial agents

Determining the in vivo bactericidal potential of novel agents is critical for selecting drug candidates. Described in this unit are two protocols that measure the amount of bacterial killing under very different conditions. The mouse pouch protocol is a rapid assay that provides efficacy data in an acute infection, whereas the rabbit tissue cage protocol assesses the ability of a compound to eradicate bacteria in a chronic abscess infection. Data from these tests, along with those from other qualitative and quantitative assays, are important for defining antibacterial efficacy in vivo.

Simultaneous determination of enrofloxacin and ciprofloxacin in animal biological fluids by high-performance liquid chromatography. Application in pharmacokinetic studies in pig and rabbit

A simple and rapid high-performance liquid chromatographic method for the simultaneous determination of enrofloxacin and ciprofloxacin has been developed in pig and rabbit samples. Solid-phase extraction was applied from samples on a C18 cartridge using a mixture of methanol-hydrochloric acid (98:2, v/v). Analytical separation was performed on a C18 column with UV detection at 277 nm under gradient conditions. The mobile phase was a mixture of orthophosphoric acidtriethylamine-acetonitrile. The method has been validated for both molecules in pig and rabbit plasma and adapted for rabbit tissue-cage fluid (TCF). The assay is specific and reproducible within the both drugs and mean recoveries for ciprofloxacin and enrofloxacin, respectively, were 92+/-6% and 90+/-5% for pig plasma over the range used. Mean recoveries for enrofloxacin were 108+/-9% and 102+/-7% for rabbit plasma and TCF, respectively, over the range used. The suitability of the assay for pharmacokinetic studies was determined by measuring enrofloxacin and ciprofloxacin concentrations either in pig plasma after administration of a single intravenous 5 mg/kg dose of enrofloxacin or in rabbit plasma and TCF during a 24 h infusion of enrofloxacin at a rate of 1.25 mg/kg per hour.

Comparison of efficacies of oral levofloxacin and oral ciprofloxacin in a rabbit model of a staphylococcal abscess

Oral levofloxacin was compared to oral ciprofloxacin in a Staphylococcus aureus subcutaneous abscess model in rabbits. Rabbits were surgically prepared with subcutaneous wiffle balls (43 mm in diameter) and allowed to recover for 4 to 6 weeks. Rabbits were infected by direct injection into the capsule with S. aureus ATCC 29213 (5 x 10(5) CFU) and were allowed to remain infected for 8 days before the initiation of anti-infective treatment. Efficacy was determined by assessing the bacterial load within the capsule over a 10-day treatment period. In single-dose pharmacokinetic studies in infected rabbits, similar area under the concentration-time curve/MIC ratios were obtained in the plasma and abscess fluid for levofloxacin at 45 mg/kg of body weight and ciprofloxacin at 200 mg/kg of body weight. Similar efficacies were seen with levofloxacin at 45 mg/kg/day and ciprofloxacin 400 mg/kg/day by day 10. In this model, levofloxacin was significantly more efficacious than ciprofloxacin (P < 0.01).

High-performance liquid chromatographic assay of cefazolin in rat tissues

A rapid, sensitive and reproducible high-performance liquid chromatographic (HPLC) assay for cefazolin in rat tissues was developed. Tissue samples were homogenized in distilled water, acidified with 8.5% phosphoric acid, and centrifuged. Cefazolin was isolated from the supernatant by solid-phase extraction on C18 cartridges. The eluate containing cefazolin and internal standard, cephalexin, was injected onto a reversed-phase C18 column and eluted with a mobile phase of 23% methanol in 0.02 M sodium phosphate monobasic (pH 5.0) and detected with UV absorbance at 270 nm. Recoveries of cefazolin were 33.7 +/- 2.5%, 45.4 +/- 2.1%, and 42.9 +/- 1.0% from liver, spleen and lung, respectively. The calibration curves for cefazolin were established at 0.5-1500 micrograms/g in spleen, 0.1-250 micrograms/g in liver and 0.1-75 micrograms/g in lung. The assay was reproducible with within-day and between-day variations of 1-2 and 1-4%, respectively. Application of the assay for tissue distribution of cefazolin in liposomal targeting study was demonstrated.

beta-Lactamase-mediated inactivation and efficacy of cefazolin and cefmetazole in Staphylococcus aureus abscesses

12694668 Clinical reports and animal models have demonstrated that cefazolin may have decreased efficacy against some strains of Staphylococcus aureus because of type A beta-lactamase-mediated hydrolysis. We sought to measure biologically active cefazolin concentrations within abscesses with high concentrations of S. aureus and compare the concentrations with those of cefmetazole, a beta-lactamase-stable cephamycin. A type A beta-lactamase-producing strain of S. aureus with a demonstrated inoculum effect against cefazolin (MIC at an inoculum of 5 x 10(5) CFU/ml, 1.0 micrograms/ml; MIC at an inoculum of 5 x 10(7) CFU/ml, 32.0 micrograms/ml) but not cefmetazole (MICs at inocula of 5 x 10(5) and 5 x 10(7) CFU/ml, 2.0 micrograms/ml) was used. Cefazolin or cefmetazole (100 mg/kg of body weight every 8 h for 8 days) was administered to rabbits with infected tissue cages. No differences in the concentrations of the two drugs in the uninfected tissue cages were observed. Higher concentrations of cefmetazole than cefazolin were found in infected tissue cages at day 3 (5.9 +/- 0.7 versus 2.2 +/- 0.3 micrograms/ml; P < 0.01), day 5 (9.1 +/- 2.6 versus 3.6 +/- 0.7 micrograms/ml; P = 0.02), and day 8 (9.4 +/- 1.4 versus 4.8 +/- 0.9 micrograms/ml; P = 0.01) after infection. Cefazolin and cefmetazole were equally effective in reducing the bacterial concentration in the abscess. In vitro experiments demonstrated greater cefazolin than cefmetazole degradation by S. aureus, but the differences were greater in serum than in abscess fluid supernatants. We conclude that abscess cefazolin concentrations are diminished by type A beta-lactamase-producing S. aureus, but this did not affect drug efficacy in this model.

Mathematical description of the concentration of oxytetracycline and penicillin-G in tissue cages in calves as related to the serum concentration

A mathematical model based on Fick's laws of diffusion describing the concentration of drug in tissue cage models was elaborated. The model takes into account differences in protein binding, tissue cage geometry and serum pharmacokinetics. The validity of the model was tested against experimental data obtained from a tissue cage model in calves by simultaneous fitting to serum and tissue cage fluid (TCF) data in a non-linear least-squares regression computer program. Concentrations of penicillin-G (pen-G) in serum and TCF following intravenous (i.v.) administration of potassium pen-G were adequately described by the mathematical model. Concentrations in TCF after intramuscular (i.m.) administration of the same drug and of procaine pen-G could be predicted by the mathematical model. Concentrations of oxytetracycline (OTC) in serum and TCF following i.v. administration and continuous i.v. infusions were also adequately described by the model, and TCF concentrations after i.m. administration of the same drug could be roughly predicted. The results indicate that pen-G and OTC have the same permeability coefficient for transport from serum to TCF.

Efficacies of various antimicrobial agents in treatment of Staphylococcus aureus abscesses and correlation with in vitro tests of antimicrobial activity and neutrophil killing

A rabbit perforated-capsule model was utilized to study antimicrobial efficacy in treating 2-week-old Staphylococcus aureus abscesses. Animals received either ciprofloxacin (30 mg/kg), cefazolin (100 mg/kg), or ciprofloxacin (30 mg/kg) plus rifampin (20 mg/kg) every 8 h for 8 days or no antibiotic. Antibiotic levels within the abscess exceeded the MIC for the test organism. At the end of treatment, ciprofloxacin was no more effective than the control, animals receiving cefazolin had a mean log10 fall of 2.41 CFU/ml, and animals receiving ciprofloxacin plus rifampin had a mean log10 reduction of 5.06 CFU/ml (P = less than 0.01). Six days after completion of therapy, all abscesses in animals receiving ciprofloxacin plus rifampin were culture negative. Surviving organisms in animals receiving ciprofloxacin or rifampin did not develop resistance to the treatment antibiotics. In vitro time-kill curves performed with logarithmic- and stationary-phase organisms in broth, serum, and abscess fluid supernatants did not correlate with the in vivo results. Neutrophil killing studies of S. aureus pretreated with antibiotics revealed greater killing of organisms pretreated with ciprofloxacin plus rifampin than of those pretreated with cefazolin or ciprofloxacin alone. In conclusion, ciprofloxacin plus rifampin was effective therapy in this staphylococcal abscess model, compared with the moderate efficacy of cefazolin and no effect observed with ciprofloxacin alone. Enhanced neutrophil killing of S. aureus pretreated with antibiotics may be an important mechanism by which bacteria are killed in suppurative infections.