A patient with hypertension and chronic kidney disease stage 3 is found to have hyperkalemia (K+ 5.6 mEq/L) on patiromer therapy. Patiromer lowers serum potassium through which mechanism?

• A Increases renal potassium excretion by upregulating ENaC channels
• B Inhibits GI potassium absorption by blocking K+/H+ ATPase in the ileum
• C Non-absorbed polymer exchanges calcium for potassium in the colon ✓
• D Binds potassium in the stomach to prevent absorption in the small intestine

Explanation

Patiromer is a non-absorbed, calcium-containing polymer that acts as a potassium binder in the colon. In the colonic lumen, it exchanges calcium ions for potassium, binding potassium tightly and preventing its absorption; the potassium-loaded polymer is then excreted in faeces. This colonic exchange (not gastric or ileal) is its mechanism. Unlike sodium polystyrene sulfonate (which exchanges sodium for potassium and has GI safety concerns), patiromer is colonic-selective and does not cause sodium loading. It does not affect renal handling of potassium and has no effect on ENaC channels.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.