Residual Proteinuria on Maximized ACE Inhibitor and SGLT2 Inhibitor
A diabetic CKD patient's proteinuria has plateaued despite both foundational drug classes already on board. A third RAAS-axis agent could push it lower — the argument is which one, or whether stacking a third agent on two already at work is worth what it costs in hyperkalemia risk.
Carlos R. has now heard the same UACR number three visits running. He is a 52-year-old man who has worked the line at the same downtown restaurant for twenty-two years, most of it on his feet through dinner service six nights a week. His type 2 diabetes, diagnosed fifteen years ago, has been the harder half of his health to manage than the hours; his UACR has come down from 1,100 mg/g to 620 mg/g since lisinopril reached its maximum tolerated dose and empagliflozin was added fourteen months ago, but it has held at roughly that level across his last three visits despite both drugs staying on board. His eGFR has been stable at 52, and his potassium has settled at 4.9 — comfortably normal on a lab report, and yet the single most consequential number in the case, because both finerenone trials required a screening potassium of 4.8 or less. Carlos misses that by a tenth of a point. He is, on the one criterion that governs the main hazard of what is being proposed, outside the population of the evidence about to be cited on his behalf.
A third agent working on the same RAAS axis could plausibly push his proteinuria lower still. Finerenone is the one with the most direct trial match: FIDELIO-DKD and FIGARO-DKD both studied it specifically as an addition to maximized ACE inhibitor or ARB therapy in diabetic CKD, and found real reductions in kidney-disease progression and cardiovascular events. Spironolactone is the older, cheaper, and far more familiar alternative in the same drug class, with its own long record of lowering proteinuria, though never tested against this exact background of concurrent SGLT2i use the way finerenone was. Both drugs work by blocking the same aldosterone receptor a fourteen-month regimen hasn't fully silenced. What neither trial can tell the group is what happens in Carlos specifically, because concurrent SGLT2 inhibitor use was uncommon in both — his empagliflozin, the drug that has done half the work on his proteinuria already, is the variable the finerenone evidence is thinnest on.
A proteinuria plateau despite two drugs already at work
Add finerenone. FIDELIO-DKD and FIGARO-DKD both studied it as an addition to maximized ACE inhibitor or ARB therapy in diabetic CKD specifically, and the reductions in both kidney-disease progression and cardiovascular events were real, not marginal. Its nonsteroidal structure gives it a materially lower hyperkalemia rate in the trial data than spironolactone carries, which matters directly given where Carlos's potassium already sits. I'll concede the awkward part before anyone raises it: at 4.9 he'd have been screened out of both trials, which set their cutoff at 4.8. The label permits initiation up to 5.0, so he remains eligible — but eligible by label and represented in the evidence are not the same thing, and he is the first without being the second.
The trial case for finerenone is strong, I won't argue against the data — but Carlos is on a high-deductible plan, and a branded specialty drug he can't reliably afford provides less real benefit over a year than a generic he actually takes every day. Spironolactone has decades of use and a real proteinuria-lowering effect of its own; I'd rather start with the drug he can sustain.
I understand the hyperkalemia-rate argument for finerenone, but his potassium today is 4.9, not already elevated — spironolactone with a monitoring plan is a manageable risk, not a disqualifying one.
Worth naming plainly: FIDELIO-DKD and FIGARO-DKD's background therapy skewed toward lower concurrent SGLT2 inhibitor use than Carlos's actual regimen, so the incremental benefit of adding either MRA on top of his specific combination isn't as directly established as the trials' headline numbers imply on their own. That's a real gap, not a reason to do nothing. But I want to be plain that the gap runs in a specific direction here. We are proposing the agent with the higher hyperkalemia signal, in a patient whose potassium already puts him outside both trials' screening threshold, on grounds that are financial rather than clinical — which can be the right call, and often is, but only if the monitoring is real. Potassium and creatinine before the first dose, at one week, at four weeks, and after any dose change or intercurrent illness; a stated stop threshold at 5.5 rather than a vague intention to watch; and dietary potassium counselling, which nobody has mentioned yet. If we cannot commit to that schedule, then affordability has not actually made spironolactone the cheaper option.
Agreed: spironolactone started at a low dose, potassium rechecked at one and four weeks, UACR reassessed at three months to confirm the proteinuria plateau actually breaks.
Not agreed: whether finerenone should become the default next step if spironolactone is either poorly tolerated or insufficiently effective, or whether cost would remain the deciding factor at that point too — left open pending how Carlos's own course actually unfolds.