How is sodium polystyrene sulfonate (SPS) in powder form prescribed for a patient with hyperkalemia?

How to Prescribe Sodium Polystyrene Sulfonate (SPS) Powder

Dosing Regimen

For non-emergent hyperkalemia, prescribe sodium polystyrene sulfonate powder at 15-60 g orally daily, typically given as 15 g (four level teaspoons) one to four times daily, or 30-50 g rectally every 6 hours. 1

Oral Administration

• Standard dosing: 15 g orally one to four times daily, with total daily doses ranging from 15-60 g depending on severity 1
• Preparation: Suspend each dose in 3-4 mL of liquid (water or syrup) per gram of resin 1
• Timing: Administer at least 3 hours before or after other oral medications (6 hours in patients with gastroparesis) due to nonselective binding that reduces absorption of other drugs 2, 1
• Position: Give with patient in upright position 1
• Preparation timing: Prepare suspension fresh and use within 24 hours; do not heat as this alters exchange properties 1

Rectal Administration

• Dosing: 30-50 g every 6 hours as a retention enema 1
• Preparation: Mix as warm (body temperature) emulsion in 100 mL aqueous vehicle, flush with 50-100 mL fluid 1
• Technique: Insert soft French 28 rubber tube 20 cm into rectum with tip in sigmoid colon; retain as long as possible, then follow with cleansing enema using up to 2 liters of non-sodium containing solution 1
• Contraindication: Avoid rectal route in neutropenic patients 2

Expected Efficacy by Dose

The potassium-lowering effect correlates directly with SPS dose:

• 15 g oral: Reduces potassium by approximately 0.39 mEq/L 3
• 30 g oral: Reduces potassium by approximately 0.69 mEq/L (or 1.25 mEq/L over 7 days) 4, 3
• 60 g oral: Reduces potassium by approximately 0.91 mEq/L 3
• 30 g rectal: Reduces potassium by only 0.22 mEq/L 3

For mild hyperkalemia (5.0-5.9 mEq/L), a 60-g oral dose is most effective as monotherapy, with 50% of patients remaining hyperkalemic after 15 g versus 23% after 60 g. 3

Critical Safety Warnings

Absolute Contraindications

• Do NOT use for life-threatening hyperkalemia or as emergency treatment due to delayed onset of action (hours to days) 2, 1
• Contraindicated in patients with hypersensitivity to polystyrene sulfonate resins, obstructive bowel disease, or neonates with reduced gut motility 1

Serious Gastrointestinal Risks

• Fatal intestinal necrosis, ischemic colitis, perforation, and bleeding have been reported with overall mortality rate of 33% in some series 2
• Risk factors include prematurity, history of intestinal disease/surgery, hypovolemia, renal insufficiency, constipation, inflammatory bowel disease, ischemic colitis, vascular intestinal atherosclerosis, previous bowel resection 1
• Never use concomitantly with sorbitol due to increased risk of colonic necrosis 5, 1
• Discontinue immediately if constipation develops 1
• Avoid in patients without bowel movement post-surgery or at risk for constipation/impaction 1

Monitoring Requirements

Monitor serum potassium, calcium, and magnesium regularly during therapy, as SPS nonselectively binds these cations. 2, 6

• Verify elevated potassium with second sample to rule out pseudohyperkalemia from hemolysis 2
• Monitor for hypokalemia, hypocalcemia, hypomagnesemia, and systemic alkalosis 2
• ECG and cardiac rhythm monitoring if potassium elevated or QRS widening present 2
• Be aware that each 15 g dose contains 1500 mg sodium 2

Common Adverse Effects

• Gastrointestinal: Constipation (8%), diarrhea, nausea, vomiting, gastric irritation 2
• Electrolyte disturbances: Hypomagnesemia, hypocalcemia, hypokalemia 2
• Metabolic: Systemic alkalosis 2
• Sodium overload: Caution in heart failure, severe hypertension, or marked edema due to sodium exchange 5

When NOT to Use SPS

Prefer Newer Potassium Binders Instead

Newer agents (patiromer or sodium zirconium cyclosilicate) are preferred over SPS for chronic hyperkalemia because they have no reported fatal gastrointestinal injury, faster onset (1-7 hours), and allow continuation of RAAS inhibitor therapy. 2

• Use newer agents for chronic hyperkalemia management in patients on maximum-tolerated RAAS inhibitor doses with potassium 5.0-6.5 mEq/L 2
• Consider alternatives for moderate hyperkalemia (6.0-6.5 mEq/L) given SPS's limited efficacy 2

Emergency Situations

• For severe hyperkalemia (>6.5 mEq/L), use emergency measures: insulin/glucose, calcium, beta-agonists, or dialysis instead of SPS 2
• For acute severe hyperkalemia, use rapid-acting treatments (calcium, insulin/glucose, nebulized albuterol) first 5, 6

Clinical Context from Guidelines

Current guidelines recommend avoiding chronic use of SPS alone or with sorbitol due to severe gastrointestinal side effects including bowel necrosis, and note that SPS has never undergone rigorous placebo-controlled testing. 5

• European Society of Cardiology guidelines suggest initiating approved potassium-lowering agents when potassium levels are confirmed >5.0 mEq/L in patients on RAAS inhibitor therapy 5
• If short-term cessation of RAAS inhibitors is necessary, minimize duration and carefully reintroduce while monitoring potassium 5