Population pharmacokinetics of nirmatrelvir/ritonavir in critically ill Chinese COVID-19 patients and recommendations for medication use: a two-center retrospective study.

Background: This study aimed to establish population pharmacokinetics (PPK) models of nirmatrelvir/ritonavir in critically ill Chinese patients with the coronavirus disease 2019 (COVID-19) infection, explore factors affecting the pharmacokinetics (PK) of nirmatrelvir/ritonavir.

Methods: A total of 285 serum samples and clinical data were collected from 152 patients. The PPK models of nirmatrelvir/ritonavir were analyzed using nonlinear mixed-effect modeling (NONMEM) approach. The optimal dosing regimen for patients with different renal function was determined using Monte Carlo simulations.

Results: The population typical values of apparent clearance (CL/F) and apparent volume of distribution (V/F) of nirmatrelvir were 2.26 L/h and 15.3 L, respectively. Notably, creatinine clearance (CrCL) significantly influenced the PK variation of nirmatrelvir. Monte Carlo simulations suggested that patients with mild-to-moderate renal impairment experienced a 22.0-59.9% increase in the area under the curve (AUC) when they were administered a standard dose of nirmatrelvir compared to those with normal renal function. The AUC in patients with severe renal impairment after administration of 150 mg q12h nirmatrelvir was similar to that in patients with normal renal function after administration of 300 mg q12h nirmatrelvir.

Conclusions: PPK modeling and simulation provided a reference for the rational clinical application of nirmatrelvir/ritonavir in critically ill Chinese patients.