Publication date: Jan 30, 2025

Nirmatrelvir/ritonavir is licensed for the treatment of mild-to-moderate coronavirus disease (COVID-19) in patients at an increased risk of progression to severe disease. However, data on the real-world plasma exposure to nirmatrelvir/ritonavir remain limited, particularly in Chinese patients. This study aimed to assess the nirmatrelvir/ritonavir trough concentration (Ctrough) and identify its critical factors in hospitalized Chinese patients treated with nirmatrelvir/ritonavir 300 mg/100 mg twice daily over a 5-day course. A high-performance liquid chromatography-tandem mass spectrometry assay was developed and validated to measure the nirmatrelvir/ritonavir Ctrough. Correlation analyses were performed to identify the variables influencing nirmatrelvir/ritonavir Ctrough. Among the 110 patients, 100% had plasma concentrations above the antiviral in vitro 90% effective concentration. The median Ctrough of nirmatrelvir was 4. 55 mcg/mL (15. 6cD7 90% effective concentration), ranging from 0. 65 to 12. 44 mcg/mL. Nirmatrelvir Ctrough in normal and mild renal impairment cohorts were comparable (4. 09 +/- 1. 97 mcg/mL and 4. 57 +/- 2. 21 mcg/mL) but significantly increased in the moderate renal impairment cohort (6. 41 +/- 2. 31 mcg/mL). Sex, age, and obesity were not significantly associated with nirmatrelvir exposure. Nirmatrelvir Ctrough was high in Chinese patients with COVID-19, and therapeutic drug monitoring should not be routinely recommended, except in patients with renal impairment.

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