Objective To evaluate the impact of continuous renal replacement therapy (CRRT) on the plasma concentration and clinical efficacy of imipenem/cilastatin in critically ill patients, and to provide a reference for optimizing individualized dosing regimens in infected patients undergoing CRRT.

Methods A retrospective analysis was conducted on patients treated with imipenem/cilastatin at the Second Affiliated Hospital of Nanjing Medical University from June 2024 to December 2025. Patients were divided into a CRRT group and a non-CRRT group based on whether they received CRRT. Baseline characteristics, imipenem dosing regimens, steady-state trough concentrations (target threshold ≥2 mg/L), and clinical outcomes were collected and compared between the two groups.

Results A total of 174 patients were enrolled in this study, including 66 patients in the CRRT group and 108 patients in the non-CRRT group. The steady-state trough serum drug concentrations were 2.84 (1.69, 4.70) mg/L in the CRRT group and 2.25 (0.91, 5.25) mg/L in the non-CRRT group, with no statistically significant difference (P > 0.05). The proportion of patients with imipenem trough concentrations below the effective target (< 2 mg/L) was 45.37% in the non-CRRT group, which was markedly higher than the 34.04% observed in the CRRT group. In the non-CRRT group, the trough serum drug concentration was significantly negatively correlated with patients' creatinine clearance (r=-0.253, P=0.008), whereas no statistically significant correlation was found in the CRRT group (P > 0.05). In the CRRT group, the median levels of PCT and CRP decreased from 7.390 ng/mL and 142.970 mg/L before treatment to 0.996 ng/mL and 69.310 mg/L after treatment, respectively. In the non-CRRT group, the median baseline PCT and CRP levels were 4.470 ng/mL and 113.400 mg/L, which declined to 0.487 ng/mL and 44.915 mg/L post-treatment. The pathogen clearance rates differed significantly between the two groups (83.87% vs. 70.49%, P < 0.05).

Conclusion The pharmacokinetics of imipenem are more complex in critically ill patients receiving CRRT, and the association between its plasma concentration and the patient's own renal function is weakened. Although the overall clinical efficacy was similar between the two groups, a significant proportion of patients in both groups failed to achieve the pharmacokinetic/pharmacodynamic (PK/PD) target. Therefore, therapeutic drug monitoring of imipenem should be actively implemented for critically ill infected patients undergoing CRRT, especially those with severe renal impairment, to achieve individualized and precise dosing based on PK/PD targets.

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