Safety and Efficacy of Finerenone in Diabetic Kidney Disease: A Single-Center Retrospective Real-World Comparative Study of Dosing and Clinical Decision-Making in Taiwan

Background: Finerenone improves cardiorenal outcomes in patients with chronic kidney disease and type 2 diabetes, but its early real-world effect on albuminuria, the relative safety and effectiveness of standard versus reduced-dose regimens, and the clinical factors influencing dose selection remain unclear. Methods: This single-center retrospective observational study included 100 patients with diabetic kidney disease: 50 received finerenone plus standard care, and 50 contemporaneous controls received standard care alone. Controls met the same eligibility criteria but were not prescribed finerenone because of physician judgment, patient preference, or financial or reimbursement considerations. UACR, serum creatinine, eGFR, and serum potassium were measured at baseline and after a mean of 28 ± 5 days (range, 21–35 days). Standard-dose finerenone was defined as 10 or 20 mg daily; reduced-dose regimens included alternate-day or intermittent weekly schedules. The principal efficacy analysis used adjusted log-transformed UACR to account for baseline imbalance and skewness. Responder, dose-stratified, post-hoc pairwise, and AIC-based model-selection analyses were exploratory. Results: Baseline characteristics were generally balanced, although baseline UACR was significantly higher in the finerenone group. In ANCOVA of log-transformed 4-week UACR adjusted for baseline ln(UACR), eGFR, serum potassium, SGLT2 inhibitor use, and ACEi/ARB therapy, finerenone was associated with lower albuminuria than usual care (adjusted geometric mean ratio, 0.73; 95% CI, 0.56–0.95; p = 0.019). The unadjusted absolute UACR change was presented descriptively. A UACR reduction of ≥30% occurred more often with finerenone than with usual care (36% vs. 14%; odds ratio, 3.46; 95% CI, 1.29–9.26; p = 0.014). Changes in serum creatinine, eGFR, and serum potassium did not differ significantly between groups. In exploratory dose-stratified analyses, standard-dose finerenone produced a greater UACR reduction than no finerenone; reduced-dose regimens did not differ significantly from no finerenone, and the direct standard- versus reduced-dose comparison did not reach conventional significance. Conclusions: Finerenone initiation was associated with lower adjusted albuminuria at four weeks. Four-week UACR assessment may support early monitoring but is not a validated threshold for treatment continuation, discontinuation, or dose escalation. No short-term safety signal was identified, although the study was not powered to assess comparative or long-term safety. Larger prospective studies are needed to determine whether early UACR changes predict long-term cardiorenal benefit.