Characteristics of ceftriaxone binding to immunoglobulin G and potential clinical significance

Pharmacokinetic/Pharmacodynamic Target Attainment Based on Measured versus Predicted Unbound Ceftriaxone Concentrations in Critically Ill Patients with Pneumonia: An Observational Cohort Study

The impact of ceftriaxone pharmacokinetic alterations on protein binding and PK/PD target attainment still remains unclear. We evaluated pharmacokinetic/pharmacodynamic (PK/PD) target attainment of unbound ceftriaxone in critically ill patients with severe community-acquired pneumonia (CAP). Besides, we evaluated the accuracy of predicted vs. measured unbound ceftriaxone concentrations, and its impact on PK/PD target attainment. A prospective observational cohort study was carried out in adult patients admitted to the intensive care unit with severe CAP. Ceftriaxone 2 g q24h intermittent infusion was administered to all patients. Successful PK/PD target attainment was defined as unbound trough concentrations above 1 or 4 mg/L throughout the whole dosing interval. Acceptable overall PK/PD target attainment was defined as successful target attainment in ≥90% of all dosing intervals. Measured unbound ceftriaxone concentrations (CEFu) were compared to unbound concentrations predicted from various protein binding models. Thirty-one patients were included. The 1 mg/L and 4 mg/L targets were reached in 26/32 (81%) and 15/32 (47%) trough samples, respectively. Increased renal function was associated with the failure to attain both PK/PD targets. Unbound ceftriaxone concentrations predicted by the protein binding model developed in the present study showed acceptable bias and precision and had no major impact on PK/PD target attainment. We showed suboptimal (i.e., <90%) unbound ceftriaxone PK/PD target attainment when using a standard 2 g q24h dosing regimen in critically ill patients with severe CAP. Renal function was the major driver for the failure to attain the predefined targets, in accordance with results found in general and septic ICU patients. Interestingly, CEFu was reliably predicted from CEFt without major impact on clinical decisions regarding PK/PD target attainment. This suggests that, when carefully selecting a protein binding model, CEFu does not need to be measured. As a result, the turn-around time and cost for ceftriaxone quantification can be substantially reduced.

Plasma and Peritoneal Ceftriaxone Concentrations After Intraperitoneal Administration in Horses With Septic Peritonitis

Intraperitoneal ceftriaxone administration in healthy horses results in high and prolonged peritoneal concentrations. Recent findings suggest that intraperitoneal ceftriaxone might increase survival rates in horses affected by peritonitis. The present study aimed to evaluate plasma and peritoneal concentrations of ceftriaxone after intraperitoneal administration in horses with septic peritonitis. Twenty-six horses presenting clinical, laboratorial, and sonographic findings compatible with the disease were included. All horses received daily intraperitoneal ceftriaxone (25 mg/kg bwt) in addition or not with other antibiotics and support therapies. High-performance liquid chromatography was used to determine plasma and peritoneal ceftriaxone concentrations before and after 12 and 24 hours of ceftriaxone administration. Mean plasma concentrations 12 and 24 hours after administration were, respectively, 1.84 ± 0.43 and 0.37 ± 0.07 μg/mL, and mean peritoneal concentrations were 5.7 ± 2.84 and 0.42 ± 0.13 μg/mL. Ceftriaxone concentration was lower in comparison with previous studies in healthy horses and presented under the minimal inhibitory concentration for enterobacteria (≤1 μg/mL) and for gram-positive isolates (≤0.5 μg/mL) at 24 hours. The variation of the results obtained between healthy horses and with septic peritonitis demonstrated that pharmacokinetics/dynamics are different between these patients and suggests the use of an interval of dose of 12 hours.

Adjuvant intraperitoneal ceftriaxone in the treatment of septic peritonitis in horses

BACKGROUND

Intraperitoneal administration of ceftriaxone maintains therapeutic abdominal concentrations for 24 hours in healthy horses. Therefore, it is a possible treatment for septic peritonitis. The aim of this study was to evaluate the efficacy of ceftriaxone as an adjuvant treatment in horses with septic peritonitis.

METHODS

Twenty-six horses with clinical signs, sonography and/or laboratory findings of septic peritonitis were included. Peritoneal fluid was collected for microbiological culture and in vitro microbial sensitivity profile assessment. Daily intraperitoneal administration of ceftriaxone (25 mg/kg) was initiated with supportive and systemic antimicrobial treatment. The animals were divided into three groups: group 1-gastrointestinal tract injuries and abdominal surgery (excluding perforations/ruptures); group 2-not related to changes in the gastrointestinal tract; group 3-secondary to intestinal rupture and/or faeces contamination.

RESULTS

The mean success rate of the treatment was 77 per cent (20/26 animals), with success rates of 84.6 per cent in group 1; 87.5 per cent, group 2; and 40 per cent, group 3.

CONCLUSIONS

This is the first study to report adjuvant intraperitoneal treatment ceftriaxone for septic peritonitis in horses and indicates that this treatment can successfully treat septic peritonitis in horses.

Influence of human serum on pharmacodynamic properties of an investigational glycopeptide, LY333328, and comparator agents against Staphylococcus aureus

The MICs and MBCs of 15 antibiotics for two strains of Staphylococcus aureus were determined in Mueller-Hinton broth (MHB) and 90% serum-10% MHB. Subsequent experiments established that highly protein-bound antibiotics (>/=80%), such as LY333328, demonstrated higher MICs and MBCs, less killing over an 8-h interval, and shorter postantibiotic effects in 90% serum-10% MHB than in MHB alone. Albumin was demonstrated to be almost solely responsible for changes in the aforementioned pharmacodynamic parameters of LY333328.