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

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.

Association of serum and fat tissue antibiotic concentrations with surgical site infections in lower gastrointestinal surgery

BACKGROUND

During surgery, the effectiveness of perioperative prophylactic antibiotic administration against surgical site infections is inferred from serum concentrations and not from tissues where local infections occur. This study aimed to measure the serum and tissue concentrations of cefmetazole in colorectal surgery cases to clarify whether there is an association between the incidence of surgical site infections and antibiotic concentrations.

METHODS

This prospective cohort study was performed at a single tertiary care center. The data of 105 patients who underwent colorectal surgery between October 2017 and September 2019 were evaluated. The primary outcome was the incidence of surgical site infections. Univariate analysis was performed to investigate the association between surgical site infections, perioperative factors, and the serum and tissue concentrations of cefmetazole.

RESULTS

The incidence of surgical site infections was 13/105 (12.4%). Cefmetazole concentrations were measured at initial incision (serum; 101 vs 93.1 mg/L, P = .75, subcutaneous fat tissue; 2.8 vs 3.7 mg/g, P = .15), intestinal resection (serum; 35.1 vs 36.7 mg/L, P = .63, mesenteric adipose tissue; 1.3 vs 1.7 mg/g, P = .55), and at skin closure (serum; 34.5 vs 44.8 mg/L, P = .18, subcutaneous fat tissue; 1.0 vs 2.2 mg/g, P = .09). In univariate analysis with P ≤ .10, cefmetazole concentration in subcutaneous fat tissue at skin closure was found to be a significant risk factor for surgical site infections. Age, additional intraoperative administration of cefmetazole, and creatinine clearance were also significant risk factors for the occurrence of surgical site infections.

CONCLUSION

Low subcutaneous fat cefmetazole concentrations at skin closure during gastrointestinal operations may also be involved in the occurrence of surgical site infections.

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.

Antibiotic Prophylaxis in Bariatric Surgical Procedures: Is There an Ideal Antimicrobial Agent?

When patients with significant comorbid risk factors undergo surgical procedures, they are at high risk for development of post-operative infectious complications, including surgical site infection (SSI). Obese patients characteristically fit within this risk category, and thus it is of paramount importance to establish evidence-based strategies to mitigate these infectious complications. The use of an antimicrobial prophylactic regimen is a well-established practice and is based on the principle of the "right drug, at the right time, in the right place." The subject of this article is to review the current evidence-based data on antimicrobial prophylaxis in obese patients undergoing bariatric surgical procedures.

Antibiotic prophylaxis with high-dose cefoxitin in bariatric surgery: an observational prospective single center study

BACKGROUND

The optimal dose of cefoxitin for antibiotic prophylaxis in obese patients remains uncertain. We evaluated the adequacy of a 4-gram dosing regimen of cefoxitin against the most frequent pathogens that infect patients undergoing bariatric surgery.

METHODS

This observational prospective study included obese patients who required bariatric surgery and a 4-gram dose of cefoxitin as an antibiotic prophylaxis. Serum concentrations were measured during surgery (incision, wound closure and in case of reinjection). The pharmacokinetic/pharmacodynamic (PK/PD) target was to obtain free cefoxitin concentrations above 4× MIC, from incision to wound closure (100% ƒT_>4xMIC). The targeted MIC was based on the worst-case scenario (the highest ECOFF value of Staphylococcus aureus, Enterobacteriaceae and anaerobic bacteria). The secondary outcomes were the factors related to underdosage.

RESULTS

Two hundred patients were included. The mean age of the patients was 46 (±12) years-old, and the mean BMI was 45.8 (±6.9) kg/m² Bypass surgery was the preferred technique (84%). The percentages of patients who met the PK/PD target (100% fT_>4xMIC) of cefoxitin were 37.3%, 1.1% and 0% for S. aureus, Enterobacteriaceae and anaerobic bacteria, respectively. BMIs below 50 kg/m² (OR 0.29, 95% CI [0.11-0.75], P = 0.0107) and a shorter duration of surgery (OR 0.97, 95% CI [0.95-0.99], P = 0.004) were associated with reaching the target concentrations.

CONCLUSIONS

In obese patients undergoing bariatric surgery, a regimen of 4 grams of cefoxitin led to an inadequate coverage for most common pathogens. A longer surgery duration and BMI over 50 kg/m² increase the risk of underdosage.

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.