Medications to Avoid in FSGS with Reduced Renal Function
Do not initiate ACE inhibitors or ARBs in patients presenting with abrupt onset nephrotic syndrome from FSGS, as these drugs can precipitate acute kidney injury, particularly when volume depleted. 1
Critical Medications to Avoid or Use with Extreme Caution
ACE Inhibitors and ARBs - Context-Dependent Avoidance
While ACE inhibitors and ARBs are generally first-line therapy for FSGS with proteinuria, there are specific situations where they must be avoided:
- Absolute avoidance: Do not start in patients with abrupt onset nephrotic syndrome, as they can cause AKI especially when patients are volume depleted 1
- Stop immediately if: Kidney function continues to worsen beyond initial 30% creatinine rise, or if refractory hyperkalemia develops 1
- Hold during illness: Counsel patients to temporarily stop ACEi/ARB and diuretics during sick days or any situation risking volume depletion 1
Calcineurin Inhibitors - GFR-Based Restriction
Avoid calcineurin inhibitors (cyclosporine, tacrolimus) when GFR is less than 40 mL/min 2. These agents carry significant nephrotoxic risk in patients with already compromised renal function and should be reserved for those with better preserved kidney function.
Cytotoxic Drugs - Limited Indications
Do not use cytotoxic drugs (cyclophosphamide, chlorambucil) unless the patient has demonstrated steroid-responsive disease 2. In patients presenting with chronic renal failure, the risk-benefit ratio is unfavorable, and these agents should generally be avoided unless there is documented prior responsiveness to steroids.
Diuretic-Related Precautions (Not Avoided, But Require Monitoring)
While diuretics are necessary for edema management, monitor closely for:
- Thiazide and loop diuretics: Risk of hypokalemia, hyponatremia (thiazides), and volume depletion especially in elderly/pediatric patients 1
- Spironolactone/eplerenone: Risk of hyperkalemia, particularly when combined with ACEi/ARB 1
- All diuretics: Can impair GFR and cause volume depletion 1
Clinical Decision Algorithm
When evaluating medication safety in FSGS with reduced renal function:
- Assess volume status first - If patient is volume depleted or at risk (acute illness, poor oral intake), hold ACEi/ARB and diuretics immediately
- Check GFR - If <40 mL/min, avoid calcineurin inhibitors
- Evaluate disease responsiveness - Only use cytotoxic drugs if prior steroid response documented
- Monitor electrolytes closely - Use potassium-wasting diuretics or binders to enable continued RAS blockade when needed 1
- Assess kidney biopsy findings - Advanced glomerulosclerosis and interstitial fibrosis/tubular atrophy make immunosuppression less likely to benefit and more likely to harm 3
Common Pitfalls
The most critical error is initiating ACEi/ARB in a patient with new-onset nephrotic syndrome who is volume depleted from massive proteinuria and diuresis. This can precipitate severe AKI. Always ensure adequate volume status before starting RAS blockade in acute presentations.