Background and Importance Ertapenem is a parenteral β-lactam antibiotic with predominantly renal excretion. It presents a time-dependent bactericidal activity and usual dose is 1g every 24h, but in patients with estimated glomerular filtration rate (eGFR) <30ml/min is recommended 0.5g every 24h.

Aim and Objectives Our aim is to evaluate the relationship between renal function (eGFR) and ertapenem plasma trough concentration (Cert).

Material and Methods Retrospective cohort study conducted at a tertiary university hospital from October 2019 to February 2021. Adult patients treated with ertapenem for at least 72 hours and who had a Cert determination were included. Biodemographic, analytical and treatment-related data were collected. Continuous variables were expressed as mean ± standard deviation (SD) and categorical variables as percentages (cases). High-performance liquid chromatography-ultraviolet (HPLC-UV) was used to measure Cert.

Cert was measured after at least two doses of ertapenem (>48h) and before the next dose administration (trough). Renal function was measured as eGFR according to CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration).

Pearson correlation coefficient (R) was calculated to study the correlation between eGFR (independent variable) and Cert (dependent variable). To determine the statistical significance of R, the analysis of variance (ANOVA) was performed and p value was obtained (IBM SPSS Statistics V21.0).

Results 102 patients with Cert determination were included, 53% male sex, with 73.0 ± 12.2 years old. Mean eGFR was 57.5 ± 27.86 mL/min/1,73 m². Cert was measured 6.4 ± 4.04 days after starting ertapenem and the mean duration of treatment was 15.5 ± 11.4 days.

R valor was -0.436 (R²=0.190) which explains an inverse linear correlation between eGFR and Cert with statistical significance (p=0.001). Influence of other covariates (albumin, platelets, ertapenem dose, sampling time) on the relationship between Cert and eGFR was studied, with no significant impact observed.

Mean Cert for the different eGFR ranges were summarised in the table:

Conclusion and Relevance

• Decrease in eGFR is correlated with an increased in Cert, with a possible overexposure in patients with renal dysfunction.

• A dose adjustment could be considered in patients with compromised renal function, even if the eGFR>30 mL/min/1,73 m².

Conflict of Interest No conflict of interest