A 55-year-old woman with CKD stage 5D on haemodialysis (3× weekly) develops hyperkalaemia (K+ 6.8 mmol/L) with peaked T waves on ECG between dialysis sessions. Which oral potassium binder approved in India/globally has a mechanism of non-absorbed sodium-free exchange in the GI tract?
- A Sodium polystyrene sulfonate (Kayexalate) exchanging K+ for Na+
- B Patiromer (a non-absorbed calcium-containing polymer exchanging K+ for Ca2+ in the colon) ✓
- C Sodium zirconium cyclosilicate (SZC) exchanging K+ for H+ and Na+ throughout the GI tract
- D Sevelamer carbonate binding K+ in addition to phosphate
Explanation
Patiromer is a non-absorbed, calcium-containing organic polymer (patiromer calcium sorbitex) that exchanges K+ for Ca2+ preferentially in the colon, lowering serum potassium. It is FDA and EMA approved for hyperkalaemia, including in CKD/dialysis patients. Sodium polystyrene sulfonate (SPS/Kayexalate) exchanges K+ for Na+, which is problematic in dialysis patients with volume overload. Sodium zirconium cyclosilicate (SZC, Lokelma) is a crystalline inorganic cation exchanger providing rapid K+ lowering (faster than patiromer) by exchanging K+ for H+/Na+ in the proximal GI tract. Sevelamer is a phosphate binder with no significant K+-binding activity. Both patiromer and SZC are preferred over SPS due to better safety profiles.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.