Objective: To assess the key factors influencing the effectiveness of nirmatrelvir/ritonavir in treating elderly patients with COVID-19.
Methods: This study was conducted on patients aged ≥ 60 who were admitted to the Second Affiliated Hospital of Soochow University for COVID-19 infection and were treated with nirmatrelvir/ritonavir. Clinical information was collected from patients and steady-state blood concentrations of nirmatrelvir and ritonavir were measured. Factors associated with treatment effects were searched by univariate and multivariate analysis.
Results: A total of 68 (51 males and 17 females) patients had a median age of 80 (73.0– 84.8) years were enrolled in this study. The blood concentration measurements (trough concentrations) of nirmatrelvir and ritonavir were 5.1 (2.6– 7.1) and 0.4 (0.2– 0.9) μg/mL, respectively. Adverse drug reaction was reported in 4 (5.9%) patients. Univariate analysis showed that age, clinical classification, APACHE II score, total bilirubin (TBil), aspartate transaminase (AST), lactate dehydrogenase (LDH), and total cholesterol (TC) were significantly associated with the effectiveness of treatment (P value < 0.05). Concentration of nirmatrelvir was also associated with treatment outcome (P value < 0.1). Based on the results of univariate analysis, the above factors were introduced into the multiple linear regression equation as independent variables, and the results showed that clinical classification was included in the regression equation model and was the most important factor affecting the treatment outcome. By receiver operating characteristic curve analysis, the area under curve of age + biochemical indicators + APACHE II score + clinical classification was 0.968 (95% CI = 0.919– 1.000; P < 0.0001). Among the 68 patients included in the study, 4 cases experienced adverse drug reactions.
Conclusion: Age, clinical classification, APACHE II score, TBil, AST, LDH, and TC were significantly associated with the effectiveness of treatment in elderly patients with COVID-19.

Keywords: nirmatrelvir/ritonavir, COVID-19, elderly patients, effectiveness