hr-810 and cefodizime

Microdialysis is a suitable method to monitor unbound concentrations of antimicrobial drugs in the interstitial tissue space which is the site of many infections. The aim of this investigation was to examine whether free tissue levels of cefodizime (81% plasma protein binding) and cefpirome (10% plasma protein binding) in muscle and subcutaneous adipose tissue of healthy volunteers obtained by microdialysis are consistent with the extent of their respective plasma protein binding. Healthy volunteers were given cefodizine and cefpirome at a single intravenous 2-g dose in a randomized crossover design. Microdialysis probes were inserted into a medial vastus muscle and into the periumbilical subcutaneous layer. After calibration of the probe, samples of serum and microdialysis fluid were obtained and drug concentrations were measured using a microagar diffusion-bioassay. There was a reasonable agreement between plasma protein binding data and the tissue penetration of both cephalosporins (AUC0-infinity tissue, free/AUC0-infinity serum, total-ratios) into the interstitial fluid of the muscle tissue, but not for the subcutaneous tissue layer. Furthermore, the serum and tissue concentrations of both drugs were fitted to an open two-compartment body model. The measured free-tissue concentrations were compared with calculated unbound concentrations in the peripheral compartment. Good agreement was observed for the free muscle concentrations, but unbound concentrations in the subcutaneous tissue was somewhat higher (cefpirome) or lower (cefodizime) than predicted. This may be due to the different lipophilicities of the two compounds.

Topics: Adipose Tissue; Adult; Area Under Curve; Cefotaxime; Cefpirome; Cephalosporins; Cross-Over Studies; Drug Monitoring; Extracellular Space; Humans; Male; Microdialysis; Muscles; Tissue Distribution

The calculation of pharmacokinetic/pharmacodynamic surrogates from concentrations in serum has been shown to yield important information for the evaluation of antibiotic regimens. Calculations based on concentrations in serum, however, may not necessarily be appropriate for peripheral-compartment infections. The aim of the present study was to apply the microdialysis technique for the study of the peripheral-compartment pharmacokinetics of select antibiotics in humans. Microdialysis probes were inserted into the skeletal muscle and adipose tissue of healthy volunteers and into inflamed and noninflamed dermis of patients with cellulitis. Thereafter, volunteers received either cefodizime (2,000 mg as an intravenous bolus; n = 6), cefpirome (2,000 mg as an intravenous bolus; n = 6), fleroxacin (400 mg orally n = 6), or dirithromycin (250 mg orally; n = 4); the patients received phenoxymethylpenicillin (4.5 x 10(6) U orally; n = 3). Complete concentration-versus-time profiles for serum and tissues could be obtained for all compounds. Major pharmacokinetic parameters (elimination half-life, peak concentration in serum, time to peak concentration, area under the concentration-time curve [AUC], and AUC/MIC ratio) were calculated for tissues. For cefodizime and cefpirome, the AUCtissue/AUCserum ratios were 0.12 to 0.35 and 1.20 to 1.79, respectively. The AUCtissue/AUCserum ratios were 0.34 to 0.38 for fleroxacin and 0.42 to 0.49 for dirithromycin. There was no visible difference in the time course of phenoxymethylpenicillin in inflamed and noninflamed dermis. We demonstrated, by means of microdialysis, that the concept of pharmacokinetic/pharmacodynamic surrogate markers for evaluation of antibiotic regimens originally developed for serum pharmacokinetics can be extended to peripheral-tissue pharmacokinetics. This novel information may be useful for the rational development of dosage schedules and may improve predictions regarding therapeutic outcome.

Topics: Adipose Tissue; Adult; Anti-Bacterial Agents; Anti-Infective Agents; Cefotaxime; Cefpirome; Cellulitis; Cephalosporins; Erythromycin; Female; Fleroxacin; Humans; Macrolides; Male; Microdialysis; Muscle, Skeletal; Skin

We developed a detailed, whole-body physiologically based pharmacokinetic (PBPK) modeling tool for calculating the distribution of pharmaceutical agents in the various tissues and organs of a human or animal as a function of time. Ordinary differential equations (ODEs) represent the circulation of body fluids through organs and tissues at the macroscopic level, and the biological transport mechanisms and biotransformations within cells and their organelles at the molecular scale. Each major organ in the body is modeled as composed of one or more tissues. Tissues are made up of cells and fluid spaces. The model accounts for the circulation of arterial and venous blood as well as lymph. Since its development was fueled by the need to accurately predict the pharmacokinetic properties of imaging agents, BioDMET is more complex than most PBPK models. The anatomical details of the model are important for the imaging simulation endpoints. Model complexity has also been crucial for quickly adapting the tool to different problems without the need to generate a new model for every problem. When simpler models are preferred, the non-critical compartments can be dynamically collapsed to reduce unnecessary complexity. BioDMET has been used for imaging feasibility calculations in oncology, neurology, cardiology, and diabetes. For this purpose, the time concentration data generated by the model is inputted into a physics-based image simulator to establish imageability criteria. These are then used to define agent and physiology property ranges required for successful imaging. BioDMET has lately been adapted to aid the development of antimicrobial therapeutics. Given a range of built-in features and its inherent flexibility to customization, the model can be used to study a variety of pharmacokinetic and pharmacodynamic problems such as the effects of inter-individual differences and disease-states on drug pharmacokinetics and pharmacodynamics, dosing optimization, and inter-species scaling. While developing a tool to aid imaging agent and drug development, we aimed at accelerating the acceptance and broad use of PBPK modeling by providing a free mechanistic PBPK software that is user friendly, easy to adapt to a wide range of problems even by non-programmers, provided with ready-to-use parameterized models and benchmarking data collected from the peer-reviewed literature.

Topics: Algorithms; Animal Structures; Animals; Biological Transport; Biotransformation; Body Fluids; Cefotaxime; Cefpirome; Cephalosporins; Computer Simulation; Contrast Media; Databases, Factual; Eukaryotic Cells; Guinea Pigs; Haplorhini; Humans; Internet; Iohexol; Mice; Models, Biological; Pharmaceutical Preparations; Pharmacokinetics; Rats; Reproducibility of Results; Software; Tissue Distribution; User-Computer Interface

Microemulsions (MEs) and mixed micelles (MMs) have been used as new drug formulations for high hydrophilic drugs such as cefpirom and cefodizim for oral administration. Cefpirom and cefodizim are neither actively nor passively transported across cell membranes. Up to date, they can be only administrated intravenously (i.v.) or intramuscularly (i.m.). The rabbit (Chinchilla) in vivo model was used in the present work to investigate ways of overcoming the poor oral absorption of these cephalosporins. The cephalosporins at 100mg/kg were formulated in MEs and MMs and administered intraduodenally (i.d.). Very low bioavailability (2.5-3.0%) was observed, if cefpirom or cefodizim i.d. were applied without colloidal vehicle. However, the addition of the cephalosporins to ME or MM is shown to be highly effective in increasing the bioavailability values (up to 64% absolute bioavailability) of the model drugs. In conclusion, MEs and MMs improve essentially the oral bioavailability of the high hydrophilic drugs.

Topics: Administration, Oral; Animals; Biological Availability; Cefotaxime; Cefpirome; Cephalosporins; Drug Carriers; Drug Compounding; Emulsions; Female; Intestinal Absorption; Micelles; Rabbits

Cephalosporins have structures and antibiotic activity similar to those of penicillins which represent a class of compounds with closely related structures. Most of the cephalosporins contain aromatic groups and show distinctive UV spectra. Separating the different types of cephalosporins is a challenging task for HPLC. but the resolving power of capillary zone electrophoresis (CZE) makes this separation fast and simple. The present study reports the application of CZE for cephalosporin analysis and the separation of cephalosporins from plasma. Both field strength and temperature were shown to influence the plate number. The influence of injection time on the peak height was studied. Furthermore, the influence of pH value on the separation of cephalosporins by CZE was investigated. The low sample amount required and the relatively short analysis time are the main advantages of this method.

Topics: Cefotaxime; Cefpirome; Cefuroxime; Cephalosporins; Electrophoresis, Capillary; Hydrogen-Ion Concentration

The inducing capacity of cefpirome (HR 810) and the ability of the compound to select for stable derepressed mutants was determined and compared with those of cefodizime (HR 221), cefotaxime, ceftazidime and cefamandol. Variations in both characteristics between and within species was observed. Overall, cefodizime showed the lowest, cefamandol the highest inducing capacity. Antibiotic resistant variants were isolated from all strains tested at a frequency of around 10(-9). A stable increased enzyme production was found in Pseudomonas aeruginosa after exposure to ceftazidime as well as in the resistant mutants from Enterobacter cloacae after selection with cefpirome, ceftazidime, cefotaxime and cefamandol. In the other resistant mutants the resistance was probably due to changes in permeability. All resistant variants remained relatively susceptible to cefpirome.

Topics: Cefotaxime; Cefpirome; Ceftazidime; Cephalosporins; Enterobacteriaceae; Microbial Sensitivity Tests; Penicillinase

Topics: Anti-Bacterial Agents; Aztreonam; Bacteria, Anaerobic; Cefotaxime; Cefpirome; Cephalosporins; Leucomycins; Microbial Sensitivity Tests