A validated LC-MS/MS method for simultaneous quantitation of piperacillin, cefazolin, and cefoxitin in rat plasma and twelve tissues.

BACKGROUND: The investigation of drug disposition in tissues is critical to improving dosing strategy and maximizing treatment effectiveness, yet developing a multi-tissue bioanalytical method could be challenging due to the differences among various matrices. Herein, we developed an LC-MS/MS method tailored for the quantitation of piperacillin (PIP), cefazolin (CFZ), and cefoxitin (CFX) in rat plasma and 12 tissues, accompanied by validation data for each matrix according to the FDA and EMA guidelines. RESULTS: The method required only a small sample volume (5 µL plasma or 50-100 µL tissue homogenates) and a relatively simple protocol for simultaneous quantitation of PIP, CFZ, and CFX within different biological matrices. Mobile phase A was composed of 5 mM ammonium formate and 0.1 % formic acid in water, while mobile phase B contained 0.1 % formic acid in acetonitrile. The mobile phase was pumped through a Synergi Fusion-RP column equipped with a guard column with a gradient elution program at a 0.3 mL/min flow rate. The mass spectrometer was operated in positive ionization mode (ESI+) using multiple reaction monitoring. SIGNIFICANCE: The validated method has been successfully applied to quantify PIP, CFZ, and CFX from the plasma and tissue samples collected in a pilot rat study and will further be used in a large pharmacokinetic study. To our knowledge, this is also the first report presenting long-term, freeze-thaw, and autosampler stability data for PIP, CFZ, and CFX in rat plasma and multiple tissues.

Population pharmacokinetics of prophylactic cefoxitin in elective bariatric surgery patients: a prospective monocentric study.

BACKGROUND: This study describes the population pharmacokinetics of cefoxitin in obese patients undergoing elective bariatric surgery and evaluates different dosing regimens for achievement of pre-defined target exposures. METHODS: Serial blood samples were collected during surgery with relevant clinical data. Total serum cefoxitin concentrations were measured by chromatographic assay and analysed using a population PK approach with Pmetrics®. The cefoxitin unbound fraction (fu) was estimated. Dosing simulations were performed to ascertain the probability of target attainment (PTA) to achieve cefoxitin fu above minimum inhibitory concentrations (MIC) from surgical incision to wound closure. Fractional target attainment (FTA) was calculated against MIC distributions of common pathogens. RESULTS: A total of 123 obese patients (median BMI 44.3 kg/m2) were included with 381 cefoxitin concentration values. Cefoxitin was best described by a one-compartment model, with a mean clearance and volume of distribution of 10.9 ± 6.1 L/h and 23.4 ± 10.5 L, respectively. In surgery <2 h, a 2 and a 4 g doses were sufficient for an MIC up to 4 and 8 mg/L (fu 50%), respectively. In prolonged surgery (2-4 h), only continuous infusion enabled optimal PTA for an MIC up to 16 mg/L. Optimal FTAs were obtained against Staphylococcus aureus and Escherichia Coli only when simulating with 50% cefoxitin protein binding (intermittent regimen) and regardless of the protein binding for the continuous infusion. CONCLUSION: Intermittent dosing regimens resulted in optimal FTAs against susceptible MIC distributions of S. aureus and E. coli when simulating with 50% cefoxitin protein binding. Continuous infusion of cefoxitin may improve FTA regardless of protein binding. STUDY REGISTRATION: Registration on ClinicalTrials.gov, NCT03306290.

Predictive performance of pharmacokinetic models for target concentration-controlled infusion of cefoxitin as a prophylactic antibiotic in patients with colorectal surgery.

We aimed to evaluate the predictive performance of previously constructed free (Cfree ) and total (Ctotal ) cefoxitin pharmacokinetic models and the possibility of administering cefoxitin via the target-controlled infusion (TCI) method in clinical practice. Two external validation studies (N = 31 for Cfree model, N = 30 for Ctotal model) were conducted sequentially. Cefoxitin (2 g) was dissolved in 50 mL of normal saline to give a concentration of 40 mg mL-1 . Before skin incision, cefoxitin was infused with a TCI syringe pump. Target concentrations of free concentration and total concentration were set to 25 and 80 µg mL-1 , respectively, which were administered throughout the surgery. Three arterial blood samples were collected to measure the total and free plasma concentrations of cefoxitin at 30, 60 and 120 min, after the start of cefoxitin administration. The predictive performance was evaluated using four parameters: inaccuracy, divergence, bias and wobble. The pooled median (95% confidence interval) biases and inaccuracies were - 45.9 (-47.3 to -44.5) and 45.9 (44.5 to 47.3) for Cfree model (Choi_F model), and - 16.6 (-18.4 to -14.8) and 18.5 (16.7 to 20.2) for Ctotal model (Choi_Told model), respectively. The predictive performance of the newly constructed model (Choi_Tnew model), developed by adding the total concentration data measured in the external validation, was better than that of the Choi_Told model. Models constructed with total concentration data were suitable for clinical use. Administering cefoxitin using the TCI method in patients maintained the free concentration above the minimal inhibitory concentration (MIC) breakpoints of the major pathogens causing surgical site infection throughout the operation period.

Influence of the Obesity Phenotype on the Adequacy of Antibiotic Prophylaxis with Cefoxitin for Obese Patients Undergoing Bariatric Surgery: Lessons Learnt and Future Considerations.

BACKGROUND AND OBJECTIVES: A high inter-individual variability in pharmacokinetic parameters in obese patients is observed. The objective of this study was to evaluate the effect of obesity parameters on the pharmacokinetics of cefoxitin administered for antibiotic prophylaxis during bariatric surgery. METHODS: This a secondary analysis of a pharmacokinetic study involving 174 obese patients scheduled for bariatric surgery and receiving a 4-g dose of cefoxitin. Blood samples were collected at incision and wound closure. The total plasma concentrations were assessed utilising a validated high-performance liquid chromatography-tandem mass spectrometry method. The pharmacokinetic and pharmacodynamic target was defined as an estimated free concentration of cefoxitin at the time of wound closure >8 mg/L. Specific evaluated obesity parameters were fat body mass, fat body mass/height2, lean body mass, lean body mass/height2, visceral adipose tissue and presence of a metabolic syndrome. RESULTS: A total of 174 patients (median age 47 years) with a majority of women (75.3%) and a median BMI of 44 kg/m2 were analysed. The percentage of patients who met the pharmacokinetic and pharmacodynamic target was 85.1%. In the whole population, a tendency to fail to reach the target was observed with a higher lean mass over height2 [OR = 0.79; 95% CI (0.62-1.01); P = 0.060]. In the female subgroup, higher lean mass over height2 [OR = 0.63; 95% CI (0.41-0.97); P = 0.037] and the presence of a metabolic syndrome [OR = 0.17; 95% CI (0.03-0.83); P = 0.030] were associated with failure to reach the pharmacokinetic and pharmacodynamic target. CONCLUSION: Obese patients with a higher lean mass and a metabolic syndrome could constitute a subgroup at risk for cefoxitin under-dosage.

Development of a new pharmacokinetic model for target-concentration controlled infusion of cefoxitin as a prophylactic antibiotic in colorectal surgical patients.

AIMS: There are several limitations to the existing method of administering cefoxitin as a prophylactic antibiotic, and the limitations may be overcome by applying the target-concentration controlled infusion (TCI) method. Population pharmacokinetic parameters are required to administer cefoxitin by the TCI method. The aim of this study was to construct a new pharmacokinetic model of cefoxitin for the TCI method in colorectal surgical patients. METHODS: In patients undergoing colorectal surgery, 2 g of cefoxitin was dissolved in 50 mL of saline and administered for 10 minutes prior to skin incision. Arterial blood samples were obtained at preset intervals to measure the total and free plasma concentrations of cefoxitin. Population pharmacokinetic analysis was performed using NONMEM software (ICON Development Solutions, Dublin, Ireland). Additionally, stochastic simulation was used to indirectly evaluate the effectiveness of the two administration methods (standard method vs TCI). RESULTS: In total, 297 plasma concentration measurements from 31 patients were used to characterize the pharmacokinetics of cefoxitin. A three-compartment mammillary model described the pharmacokinetics of cefoxitin. Body weight and creatinine clearance were significant covariates for clearance. The stochastic simulation showed that when compared with the standard method, the TCI method has a significantly higher fraction of time that the free concentration of cefoxitin is maintained above the minimum inhibitory concentration (P < .001). CONCLUSIONS: TCI has the potential to become a new infusion method for patient-tailored dosing in surgical patients. To administer cefoxitin via TCI in clinical practice, the newly constructed pharmacokinetic model should undergo proper external validation.

Population Pharmacokinetics of Cefoxitin Administered for Pediatric Cardiac Surgery Prophylaxis.

BACKGROUND: Available data about pharmacokinetics (PK) of antimicrobials administered as surgical prophylaxis to children undergoing cardiac surgery with cardiopulmonary bypass (CPB) showed that drug concentrations during CPB may be supra or subtherapeutic. The aim of this study was to determine the population PK and pharmacodynamic target attainment (PTA) of cefoxitin during pediatric CPB surgery. METHODS: A prospective interventional study was conducted. Cefoxitin (40 mg/kg, up to max 1000 mg) was administered before skin incision. Blood samples were obtained in the operatory room throughout surgery. Population PK, PTA, and safety of cefoxitin were evaluated in neonates, infants, children <10 and >10 years old. RESULTS: Forty patients were enrolled. Cefoxitin levels correlated with time from bolus administration (r = -0.6, P = 0.0001) and, after 240 minutes from bolus, drug values below the target (8 mg/L) were shown. Cefoxitin concentrations were best described by a one-compartment model with first order elimination. A significant relationship was identified between body weight, age, body mass index, and serum creatinine on drug clearance and age, body weight, and body mass index on cefoxitin volume of distribution. The PTA for free drug concentration being above the minimum inhibitory concentration of 8 mg/L for at least 240 minutes was >90% in all age groups except in patients >10 years of age (PTA = 62%). CONCLUSIONS: Cefoxitin PK appears to be significantly influenced by CPB with generally reduced drug clearance. The PTA was adequately achieved in the majority of patients except in patients >10 years old or longer surgeries.

Reassessing the dosing of cefoxitin prophylaxis during major abdominal surgery: insights from microdialysis and population pharmacokinetic modelling.

OBJECTIVES: Cefoxitin is frequently used for surgical antibiotic prophylaxis (SAP). Using microdialysis, we evaluated whether the currently recommended dosing regimen is appropriate to maintain cefoxitin subcutaneous tissue concentrations above the MIC for pathogens involved in abdominal surgical site infection. METHODS: Data from eight patients undergoing major abdominal surgery were analysed using population pharmacokinetic modelling, and Monte Carlo simulations were conducted to determine the PTA for aerobic and anaerobic pathogens. ClinicalTrials.gov: NCT02703857. RESULTS: Only 2.3% and 47.4% of the simulated patients maintained cefoxitin subcutaneous concentrations above the MIC breakpoint for anaerobic (MIC = 16 mg/L) and aerobic (MIC = 8 mg/L) pathogens, respectively. New simulations with administration of a loading dose followed by a constant infusion of cefoxitin were conducted and demonstrate that, notwithstanding using the same total dose per unit of time, continuous infusion of cefoxitin can cover aerobes in 96.6% of the simulated patients, but remains insufficient for anaerobic bacteria. CONCLUSIONS: The recommended dosing regimen of cefoxitin is insufficient for covering the usual bacteria during abdominal surgery. Administration of a loading dose followed by a constant infusion should be considered for aerobic bacteria and cefoxitin should be avoided as SAP for anaerobic bacteria.

Preclinical Pharmacokinetic and Pharmacodynamic Data To Support Cefoxitin Nebulization for the Treatment of Mycobacterium abscessus.

Mycobacterium abscessus is responsible for difficult-to-treat chronic pulmonary infections in humans. Current regimens, including parenteral administrations of cefoxitin (FOX) in combination with amikacin and clarithromycin, raise compliance problems and are frequently associated with high failure and development of resistance. Aerosol delivery of FOX could be an interesting alternative. FOX was administered to healthy rats by intravenous bolus or intratracheal nebulization, and concentrations were determined in plasma and epithelial lining fluid (ELF) by liquid chromatography-tandem mass spectrometry. After intrapulmonary administration, the FOX area under the curve within ELF was 1,147 times higher than that in plasma, indicating that this route of administration offers a biopharmaceutical advantage over intravenous administration. FOX antimicrobial activity was investigated using time-kill curves combined with a pharmacokinetic/pharmacodynamic (PK/PD) type modeling approach in order to account for its in vitro instability that precludes precise determination of MIC. Time-kill data were adequately described by a model including in vitro degradation, a sensitive (S) and a resistant (R) bacteria subpopulation, logistic growth, and a maximal inhibition-type growth inhibition effect of FOX. Median inhibitory concentrations were estimated at 16.2 and 252 mg/liter for the S and R subpopulations, respectively. These findings suggest that parenteral FOX dosing regimens used in patients for the treatment of M. abscessus are not sufficient to reduce the bacterial burden and that FOX nebulization offers a potential advantage that needs to be further investigated.

Cefoxitin Prophylaxis During Pediatric Cardiac Surgery: Retrospective Exploration of Postoperative Trough Levels.

BACKGROUND: This study aimed to explore inter-individual variability of cefoxitin trough levels, predictors of serum cefoxitin concentration and the probability of target attainment of drug levels above 4 mg/L after pediatric cardiac surgery. METHODS: Retrospective study on children scheduled for elective cardiac surgery and having cefoxitin trough levels available up to 24 hours postsurgery. RESULTS: Overall, 68 children (9 neonates, 34 infants, 15 children below or equal to 10 years old and 10 patients above this age) were included. Of these, 16 surgeries were performed off cardiopulmonary bypass and 52 were performed on cardiopulmonary bypass. The free cefoxitin concentrations showed a median (interquartile range) concentration of 1.7 (0.6-4.2) mg/L. The range of cefoxitin concentrations showed a 150-fold and 340-fold variability at cardiac intensive care unit admission and after 24 hours, respectively. The pharmacodynamics (PD) targets of free cefoxitin at 100% of the dosing interval, considering Eucast breakpoints for Methicillin Sensitive Staphylococcus Aureus (4 mg/L) and E.Coli (8 mg/L), were obtained in 28% and 16% of patients, respectively. Patient weight (odds ratio, 0.7; 95% confidence interval, 0.62-0.92; P = 0.006) and serum creatinine concentrations (odds ratio, 25; 95% confidence interval, 18-36; P = 0.004) showed a significant relationship with the PD targets. CONCLUSIONS: Cefoxitin trough concentrations vary significantly in the first 24 hours after pediatric cardiac surgery. Both serum creatinine and body weight showed independent associations with cefoxitin concentration. The PD target was not obtained in the vast majority of the explored population, regardless of the target bacteria.

Pharmacokinetic and Pharmacodynamic Evaluation of a Weight-Based Dosing Regimen of Cefoxitin for Perioperative Surgical Prophylaxis in Obese and Morbidly Obese Patients.

The objective of this study was to determine the pharmacokinetics and pharmacodynamics (PK/PD) of a weight-based cefoxitin dosing regimen for surgical prophylaxis in obese patients. Patients received a single dose of cefoxitin at 40 mg/kg based on total body weight. Cefoxitin samples were obtained over 3 h from serum and adipose tissue, and concentrations were determined by validated high-performance liquid chromatography. Noncompartmental pharmacokinetic analysis was performed, followed by Monte Carlo simulations to estimate probability of target attainment (PTA) for Staphylococcus aureus, Escherichia coli, and Bacteroides fragilis over 4-h periods postdose. Thirty patients undergoing bariatric procedures were enrolled. The body mass index (mean ± standard deviation [SD])was 45.9 ± 8.0 kg/m(2) (range, 35.0 to 76.7 kg/m(2)); the median cefoxitin dose was 5 g (range, 4.0 to 7.5 g). The mean maximum concentrations were 216.15 ± 41.80 µg/ml in serum and 12.62 ± 5.89 in tissue; the mean tissue/serum ratio was 8% ± 3%. In serum, weight-based regimens achieved ≥90% PTA (goal time during which free [unbound] drug concentrations exceed pathogen MICs [fT>MIC] of 100%) for E. coli and S. aureus over 2 h and for B. fragilis over 1 h; in tissue this regimen failed to achieve goal PTA at any time point. The 40-mg/kg regimens achieved higher PTAs over longer periods in both serum and tissue than did the standard 2-g doses. However, although weight-based cefoxitin regimens were better than fixed doses, achievement of desired pharmacodynamic targets was suboptimal in both serum and tissue. Alternative dosing regimens and agents should be explored in order to achieve more favorable antibiotic performance during surgical prophylaxis in obese patients.

Cefoxitin Plasma and Subcutaneous Adipose Tissue Concentration in Patients Undergoing Sleeve Gastrectomy.

PURPOSE: Antibiotic dosing in obese surgical patients has not been adequately evaluated. The objective of this study was to identify whether currently prescribed doses of cefoxitin achieve adequate and sustained plasma and tissue concentrations in obese patients undergoing sleeve gastrectomy. METHODS: A prospective evaluation of plasma and tissue cefoxitin concentrations in patients undergoing sleeve gastrectomy was performed. On the day of the surgical procedure, venous blood samples (5 mL) were collected just before cefoxitin administration and then at 5, 30, 60, 120, and 240 minutes after dose administration. In addition, subcutaneous adipose tissue was collected from the surgical site at the time of surgical incision and at closure. Cefoxitin concentrations in the collected samples were quantified by using an HPLC-ultraviolet method. A standard noncompartmental analysis was performed for each individual cefoxitin plasma concentration-time profile. In addition, the ratio of tissue to plasma concentration was calculated for all patients. FINDINGS: Plasma and tissue pharmacokinetics of cefoxitin were evaluated in 6 patients undergoing sleeve gastrectomy. The mean age and BMI were 48.7 (6.2) years and 42.8 (7.1) kg/m(2), respectively. At the time of surgical closure, subcutaneous adipose tissue concentrations of cefoxitin were subtherapeutic (<8 µg/mL) in all evaluated patients. IMPLICATIONS: Current dosing strategies for cefoxitin in obese surgical patients may be inadequate, and there is an urgent need to define the appropriate dosage.

Pharmacological study of cefoxitin as an alternative antibiotic therapy to carbapenems in treatment of urinary tract infections due to extended-spectrum-ß-lactamase-producing Escherichia coli.

Cefoxitin could be an alternative to carbapenems in extended-spectrum-beta-lactamase-producing Escherichia coli (ESBL-EC) infections. However, pharmacological and clinical data regarding cefoxitin are limited. Using a recent pharmacological model and the MICs of ESBL-EC collected from pyelonephritis, we determined the probabilities to reach four pharmacological targets: free cefoxitin concentrations above the MIC during 50% and 100% of the administration interval (T>MIC = 50% and T>MIC = 100%, respectively) and free cefoxitin concentrations above 4× MIC during 50% and 100% of the administration interval (T>4MIC = 50% and T>4MIC = 100%, respectively). Cefoxitin could be used to treat ESBL-EC pyelonephritis, but administration modalities should be optimized according to MICs in order to reach pharmacological targets.

Population pharmacokinetics of prophylactic cefoxitin in patients undergoing colorectal surgery.

PURPOSE: To elucidate whether a dose of 2 g cefoxitin as a prophylactic agent in patients undergoing elective colorectal surgery is able to maintain free drug concentrations above the minimum inhibitory concentration of the microorganisms involved in surgical site infection. METHODS: This was a prospective study involving 56 patients electively undergoing rectal or colon surgery. All plasma concentration-time data were analyzed simultaneously using the population approach to estimate population pharmacokinetic parameters and study the influence of the subjects' demographic characteristics, disease status, surgical procedure, and clinical laboratory values on the pharmacokinetic properties of cefoxitin. RESULTS: A one-compartment open model was chosen to describe plasma concentrations of cefoxitin. Since cefoxitin is eliminated almost entirely via the kidney, creatinine clearance was identified as a covariate of cefoxitin clearance. The relationship between total cefoxitin clearance (CL) and creatinine clearance (CL(CR)) was best described using a nonlinear model [CL = 11.5 × (CL(CR)/77)(0.52)]. The population apparent volume of distribution was 12 L. Computer simulations carried out to determine the probability to maintain free plasma concentrations above 8 mg/L (the concentration threshold for susceptible bacteria) 2 h after drug administration revealed that this probability decreased from 84% in patients with a CL(CR) of 40 mL/min to 28% in patients with a CL(CR) of 100 mL/min. CONCLUSIONS: To ensure cefoxitin target concentrations during surgery, we recommend that cefoxitin be administered every 1.5 h in patients with a CL(CR) ≥ 60 mL/min and every hour if the CL(CR) is ≥ 100 mL/min. Administration by continuous infusion preceded by a bolus injection should also be considered.

Pharmacokinetics and tissue penetration of cefoxitin in obesity: implications for risk of surgical site infection.

BACKGROUND: Obesity is a significant risk factor for surgical site infections (SSIs), for poorly understood reasons. SSIs are a major cause of morbidity, prolonged hospitalization, and increased health care cost. Drug disposition in general is frequently altered in the obese. Preoperative antibiotic administration, achieving adequate tissue concentrations at the time of incision, is an essential strategy to prevent SSIs. Nonetheless, there is little information regarding antibiotic concentrations in obese surgical patients. This investigation tested the hypothesis that the prophylactic antibiotic cefoxitin may have delayed and/or diminished tissue penetration in the obese. METHODS: Plasma and tissue concentrations of cefoxitin were determined in obese patients undergoing abdominal and pelvic surgery (body mass index 43 ± 10 kg/m(2), n = 14, 2 g cefoxitin) and in normal-weight patients and healthy volunteers (body mass index 20 ± 2 kg/m(2), n = 13, 1 g cefoxitin). Tissue concentrations were measured using a microdialysis probe in the subcutaneous layer of the abdomen, and in adipose tissue excised at the time of incision and wound closure. RESULTS: Plasma concentrations and area under the concentration-time curve (AUC) were approximately 2-fold higher in the obese patients because of the 2-fold-higher dose. Dose-normalized concentrations were higher, although AUCs were not significantly different. Measured and dose-normalized subcutaneous cefoxitin concentrations and AUCs in the obese patients were significantly lower than in the normal-weight subjects. There was an inverse relationship between cefoxitin tissue penetration (AUC(tissue)/AUC(plasma) ratio) and body mass index. Tissue penetration was substantially lower in the obese patients (0.08 ± 0.07 vs 0.37 ± 0.26, P < 0.05). Adipose tissue cefoxitin concentrations in obese patients were only 7.8 ± 7.3 and 2.7 ± 1.4 µg/g, respectively, at incision and closure, below the minimum inhibitory concentration of 8 and 16 µg/mL, respectively, for aerobic and anaerobic microorganisms. CONCLUSION: Obese surgical patients have impaired tissue penetration of the prophylactic antibiotic cefoxitin, and inadequate tissue concentrations despite increased clinical dose (2 g). Inadequate tissue antibiotic concentrations may be a factor in the increased risk of SSIs in obese surgical patients. Additional studies are needed to define doses achieving adequate tissue concentrations.

Desenvolvimento e Caracterização de Nanopartículas de D, L-PLA contendo Cefoxitina / Development and Characterization of Cefoxitin Loaded D, L-PLA Nanoparticles

As nanopartículas de D, L-PLA (PLA) contendo cefoxitina (CEF) foram preparadas pelo método de emulsão múltipla / evaporação do solvente. As partículas foram avaliadas em relação à morfologia, à eficiência de encapsulação, às interações polímero-fármaco, bem como à cinética de liberação do fármaco in vitro . As nanopartículas são esféricas e isoladas, com um diâmetro médio de cerca de 600 nm. O comportamento térmico (DSC) das nanopartículas contendo CEF sugeriu que o fármaco está disperso em um nível molecular dentro do sistema. A eficiência de encapsulação do fármaco no sistema quando a concentração de CEF é 30 mg / mL foi de 5,5%, determinada após a extração de fármaco, através de um método de HPLC validado. Esta baixa eficiência de encapsulação é compreensível, uma vez que a CEF é altamente hidrofílica. Os ensaios in vitro mostraram um perfil de liberação do fármaco a partir das nanopartículas fortemente sustentado e com uma cinética de difusão Fickiana pura.

Nanoparticles containing cefoxitin (CEF) made of D,L-PLA (PLA) were designed by a multiple emulsion/solvent evaporation method. The particles were extensively evaluated in relation to morphology, encapsulation efficiency, drug-polymer interactions as well as in vitro drug release kinetics. Nanoparticles were spherical in shape and isolated, with a mean diameter of about 600 nm. The thermal behaviour (DSC) of CEF-containing nanoparticles suggested that the drug was dispersed at a molecular level within the system. The drug encapsulation efficiency in the system for a CEF concentration of 30 mg/mL was 5.5%, as assessed after the drug extraction, by a validated HPLC method. This low encapsulation efficiency is understandable, since CEF is highly hydrophilic. The in vitro assays showed a strong sustained drug release profile from the nanoparticles with kinetics following pure Fickian diffusion.

The characterization and biodistribution of cefoxitin-loaded liposomes.

To conquer the clinical restriction of relative short half-life and poor tissue retaining activities, liposomes containing cefoxitin were prepared using three methods in this study. The physicochemical properties including cefoxitin encapsulation percentage, vesicle size, stability, as well as the in vivo biodistribution were studied. The highest entrapment percentage was observed by using reverse phase evaporation method, and the molar ratio of cefoxitin to phospholipids was 1:3, DMPC to cholesterol was 2:1, respectively. From the result of stability, the freeze-drying powder and then stored in the frozen condition of cefoxitin-loaded liposome was an ideal storage state. Accordingly, the formulation by reverse-phase evaporation method was selected to investigate the biodistribution of cefoxitin-loaded liposome and compared to free cefoxitin in rats. It was observed that the cefoxitin levels and the duration retained in the liver, spleen, and pancreas of liposome-injected animals were higher and longer than that of free cefoxitin-injected animals. The drug concentrations of bile after post-injection of liposomal cefoxitin at 0.5, 1 and 2 h were all approximately 2.7 times higher than that of free cefoxitin injection group.

Liposomal entrapment of cefoxitin to improve cellular viability and function in human saphenous veins.

Liposomal cefoxitin was prepared and applied to the pretreatment of human saphenous vein (HSV) for implantation. The possible use of liposomal cefoxitin to improve cellular viability and function and to maintain its potential sterilization effect was investigated. Entrapment efficiency and size distribution of liposomal cefoxitin were 75.7% and 652 +/- 75.7 nm, respectively. The weight ratio between cefoxitin and liposome was calculated at 1 : 40.6. When cefoxitin was entrapped with liposome, the released amount of cefoxitin was not affected by temperature conditions (37 degrees C, 25 degrees C, and 4 degrees C). The amount of free cefoxitin present in HSV reached 59% at 0.5 h and gradually decreased with time, while liposomal cefoxitin showed a maximum amount (63%) at 1.5 h, indicating that liposomal cefoxitin seemed to control the initial amount of cefoxitin present in HSV. Liposomal cefoxitin showed better viabilities of whole cells and endothelial cells dissociated from HSV than free cefoxitin and remarkably superior function of endothelial cells, as determined by Griffonia simplicifolia agglutinins-fluorescein isothiocyanate/propidium iodide double-staining methods combined with flow cytometry and endothelial nitric oxide synthase assay, respectively. In terms of sterilization effect, there was no significant difference between liposomal cefoxitin and free cefoxitin. These results suggest that liposomal entrapment of cefoxitin could improve cellular viability and functions and maintain the original sterilization effect.

Distribution of free and liposomal cefoxitin in plasma and peritoneal fluid in a porcine intra-abdominal sepsis model.

The plasma and peritoneal fluid pharmacokinetic parameters obtained after the intravenous administration of free and liposomal cefoxitin were studied in a porcine model of intraabdominal sepsis. No prior assumptions were made to predict the number of compartments pertaining to drug clearance from the administration of either cefoxitin formulation. The experimental data obtained were applied to fit mathematical models of multiexponential drug clearance and the pharmacokinetic data were found to best fit a two-compartment open model. Liposomal encapsulation significantly altered the plasma drug distribution pattern resulting in changes in the magnitude of a number of pharmacokinetic parameters examined. The mean post-distributive half-life of liposomal cefoxitin was substantially longer than that of free cefoxitin by at least 3 times. The peritoneal cavity appeared to provide a reservoir for the initial distributive phase of rapid drug clearance from the plasma compartment followed by a less-rapid post-distributive phase. The cumulative drug level, as determined by the area under the concentration curve (AUC) as a function of time, in the plasma of animals treated with liposomal cefoxitin was about 3-4 fold as high as that of animals treated with free cefoxitin. The differences in pharmacokinetic parameters appeared to account for the improved therapeutic efficacy of liposomal cefoxitin in this animal model.

The enhancing mechanism of capric acid (C10) from a suppository on rectal drug absorption through a paracellular pathway.

Capric acid (C10) enhanced the absorption of cefoxitin sodium in a concentration-dependent manner following the rectal administration as a suppository in rats. The optimal concentration of C10 was 13%. C10 administered as a suppository also reduced rectal membrane resistance (Rm), showing that the above enhancing effect was induced by widening the paracellular pathway. Both the enhancing effect on the absorption and the reducing effect on Rm were inhibited by W7, an inhibitor of myosin light chain kinase. These results supported that, as shown in the in vitro Caco-2 cell system, the C10 effect on the paracellular pathway is due to activating the contraction of Ca(2+)-calmodulin-dependent actin filament.