Safety, efficacy, and pharmacokinetics of nirmatrelvir and ritonavir in patients with severe COVID-19 and renal impairment: A case report.

Nirmatrelvir/ritonavir (N/r) has received emergency use authorization for mild-to-moderate COVID-19 treatment in adult and pediatric patients (aged and weighing at least 12 years and 40 kg, respectively) presenting positive direct SARS-CoV-2 viral testing results and a high risk of disease progression to severe COVID-19. However, information remains limited concerning the corresponding drug safety, efficacy, and pharmacokinetics in patients with severe renal impairment. In this study, we present the case of a 91-year-old Chinese man who, despite exhibiting recurrent positive SARS-CoV-2 results and progression to severe COVID-19, was treated with N/r. Due to severe renal impairment and concurrent administration of continuous renal replacement therapy (continuous venovenous hemofiltration) during medication, we aimed to determine the serum N/r drug concentration in the patient. Our analysis revealed Cmax values of 12.42 and 2.001 μg/mL for nirmatrelvir and ritonavir, respectively. Despite the particularly high serum N/r concentration in this patient, the clinical and laboratory test analyses confirmed that the treatment was safe and effective. Nevertheless, N/r should be used with caution and at lower doses in patients with severe renal impairment to avoid potential high N/r concentration-related adverse reactions and events.