What is the recommended dosing of Kayexalate (sodium polystyrene sulfonate) for a patient with hyperkalemia?

Kayexalate Dosing for Hyperkalemia

For non-emergent hyperkalemia, administer Kayexalate (sodium polystyrene sulfonate) 15-60 g orally daily (typically 15 g one to four times daily) or 30-50 g rectally every 6 hours, but never use it for life-threatening hyperkalemia due to its delayed onset of action. 1, 2

Specific Dosing Regimens

Oral Administration

• Standard dose: 15 g (four level teaspoons) administered one to four times daily, with total daily dose ranging from 15-60 g 2
• Suspend each dose in 3-4 mL of liquid per gram of resin (water or syrup) 2
• Administer with patient in upright position 2
• One level teaspoon contains approximately 3.5 g of sodium polystyrene sulfonate and 15 mEq of sodium 2

Rectal Administration

• Dose: 30-50 g every 6 hours as a warm enema 1, 2
• Administer as warm emulsion in 100 mL aqueous vehicle, flush with 50-100 mL fluid 2
• Retain resin as long as possible, then follow with cleansing enema using up to 2 liters of non-sodium containing solution 2
• Avoid rectal administration in neutropenic patients 1

Critical Timing and Separation Requirements

• Separate Kayexalate from other oral medications by at least 3 hours (6 hours in patients with gastroparesis) due to nonselective binding that reduces absorption of other drugs 1, 2
• Prepare suspension fresh and use within 24 hours 2
• Do not heat the resin as it alters exchange properties 2

When NOT to Use Kayexalate

Kayexalate is contraindicated as emergency treatment for life-threatening hyperkalemia because onset of action takes several hours to days 3, 4, 1, 2

Use Rapid-Acting Treatments Instead for Severe Hyperkalemia:

• Calcium (for cardiac membrane stabilization) 4, 1
• Insulin with glucose 4, 1
• Nebulized albuterol 4, 1
• Dialysis for refractory cases 1

Absolute Contraindications:

• Obstructive bowel disease 2
• Neonates with reduced gut motility 2
• Hypersensitivity to polystyrene sulfonate resins 2

Avoid Use in High-Risk Patients:

• Patients without bowel movement post-surgery 2
• History of constipation, impaction, or inflammatory bowel disease 2
• Ischemic colitis or vascular intestinal atherosclerosis 2
• Previous bowel resection or obstruction 2

Expected Efficacy

• In mild hyperkalemia (K+ 5.0-5.9 mEq/L), 30 g daily for 7 days reduces serum potassium by approximately 1.04 mEq/L more than placebo 3
• The practical exchange ratio is 1 mEq potassium per 1 gram of resin 4
• Onset of action is variable, typically several hours to days 4, 1

Critical Safety Monitoring

Required Laboratory Monitoring:

• Monitor serum potassium regularly to prevent severe hypokalemia 1, 2
• Monitor calcium and magnesium levels because Kayexalate nonselectively binds these cations, causing hypocalcemia and hypomagnesemia 4, 1, 2
• Verify elevated potassium with second sample to rule out pseudohyperkalemia from hemolysis 1
• Monitor ECG and cardiac rhythm, especially if QRS widening present 1

Serious Gastrointestinal Risks:

• Fatal intestinal necrosis, ischemic colitis, perforation, and bleeding have been reported with overall mortality rate of 33% in some series 1
• Never administer concomitantly with sorbitol due to increased risk of colonic necrosis 1, 2, 5, 6, 7, 8
• Colon is the most commonly affected site (76.3% of cases) 7
• Average time to gastrointestinal adverse events is 19.8 days 7
• Discontinue immediately if constipation develops 2

Common Adverse Effects:

• Constipation (8%), diarrhea, nausea, vomiting, gastric irritation 1
• Systemic alkalosis 1
• Each 15 g dose contains 1500 mg sodium (consider in volume-sensitive patients) 1

Preferred Alternative Agents

For chronic hyperkalemia management, newer potassium binders (patiromer or sodium zirconium cyclosilicate) are preferred because they have: 1

• No reported cases of fatal gastrointestinal injury 1
• Faster onset of action (1-7 hours vs hours to days) 1
• Better tolerability 3
• Allow continuation of RAAS inhibitor therapy 1

These alternatives are particularly preferred for: 1

• Patients requiring chronic potassium management
• Those on maximum-tolerated RAAS inhibitor doses with potassium 5.0-6.5 mEq/L
• Moderate hyperkalemia (6.0-6.5 mEq/L) where Kayexalate has limited efficacy