How do phosphate binders help CKD patients and when should they be taken?

• A. They bind dietary phosphate in the GI tract to reduce absorption; taken with meals
• B. They increase phosphate absorption in the gut; taken with meals
• C. They bind potassium
• D. They replace phosphate losses in urine

Answer: (A)

Phosphate binders work by preventing dietary phosphate from being absorbed in the gut, which helps lower serum phosphate in CKD when the kidneys can’t excrete it well. They bind phosphate in the intestinal lumen and form insoluble complexes that are eliminated in the stool. Because their job is to intercept phosphate as it’s consumed, they must be taken with meals (or with each meal) so they are present in the gut when dietary phosphate is ingested. They don’t increase phosphate absorption, they don’t bind potassium, and they don’t replace phosphate losses in urine.