What is the treatment for hyperkalemia using Sodium polystyrene sulfonate?

Treatment of Hyperkalemia with Sodium Polystyrene Sulfonate

Sodium polystyrene sulfonate (SPS) is indicated for the treatment of hyperkalemia, but should not be used as an emergency treatment for life-threatening hyperkalemia due to its delayed onset of action. 1

Mechanism of Action and Pharmacology

Sodium polystyrene sulfonate is a cation-exchange resin that:

• Binds potassium ions in exchange for sodium ions primarily in the distal colon
• Has nonselective binding properties (also binds calcium and magnesium)
• Has a variable onset of action (several hours)
• Contains 1500 mg of sodium per 15 g dose
• Contains 20,000 mg of sorbitol per 15 g dose 2

Dosage and Administration

Oral Administration

• Average adult dose: 15-60 g daily
• Typically administered as 15 g (four level teaspoons) 1-4 times daily
• Suspend each dose in 3-4 mL of water or syrup per gram of resin
• Administer with patient in upright position 1

Rectal Administration

• Average adult dose: 30-50 g every six hours
• Administer as a warm emulsion in 100 mL of aqueous vehicle
• Flush with 50-100 mL of fluid
• Should be retained as long as possible and followed by a cleansing enema 1

Important Administration Considerations

• Administer at least 3 hours before or 3 hours after other oral medications
• Patients with gastroparesis may require a 6-hour separation
• Prepare suspension fresh and use within 24 hours
• Do not heat SPS as it could alter the exchange properties 1

Clinical Efficacy

In a randomized, double-blind, placebo-controlled trial of patients with CKD and mild hyperkalemia:

• SPS 30 g daily for 7 days reduced serum potassium by 1.25 mEq/L compared to 0.21 mEq/L with placebo
• Mean difference between groups was 1.04 mEq/L (95% CI: 1.37 to 0.71 mEq/L; p<0.001) 2, 3

However, in a retrospective observational study:

• SPS reduced serum potassium by only 0.14 mmol/L more than control
• This small treatment effect may not be clinically significant for mild hyperkalemia 4

Safety Concerns and Adverse Events

SPS has been associated with serious adverse events:

• Intestinal ischemia and colonic necrosis (some fatal)
• Doubling in risk of hospitalization for serious gastrointestinal adverse events
• Reported overall mortality rate of 33% 2

Common adverse effects include:

• Gastrointestinal disorders (constipation, diarrhea, nausea, vomiting, gastric irritation)
• Electrolyte disturbances (hypomagnesemia, hypokalemia, hypocalcemia)
• Systemic alkalosis 2

Contraindications

SPS is contraindicated in patients with:

• Hypersensitivity to polystyrene sulfonate resins
• Obstructive bowel disease
• Neonates with reduced gut motility 1

Clinical Recommendations Based on Severity of Hyperkalemia

Mild to Moderate Hyperkalemia (K+ 5.0-5.9 mEq/L)

• SPS may be initiated at 15 g 1-4 times daily
• Monitor potassium levels closely
• Consider alternative K+-binding agents (patiromer or sodium zirconium cyclosilicate) if available 2

Severe Hyperkalemia (K+ >6.0 mEq/L)

• SPS should not be used as first-line therapy due to delayed onset of action
• Emergency measures should be implemented first (calcium gluconate, insulin with glucose, beta-agonists)
• Once stabilized, SPS can be used for ongoing management 2, 5

Patients on RAAS Inhibitors

• For K+ levels >5.0 to 6.5 mEq/L: Initiate K+-lowering therapy while maintaining RAAS inhibitors if possible
• For K+ levels >6.5 mEq/L: Discontinue or reduce RAAS inhibitor therapy; K+-lowering therapy may be started when K+ >5.0 mEq/L 2

Monitoring Recommendations

• Measure serum potassium within 1 week of starting treatment
• Monitor more frequently in patients with CKD, heart failure, or diabetes
• Also monitor serum sodium, calcium, and magnesium due to nonselective binding properties of SPS 2, 5

Important Precautions

• Avoid use in patients at risk for developing constipation or impaction
• Discontinue use in patients who develop constipation
• Use only in patients with normal bowel function
• Concomitant administration of sorbitol is not recommended due to increased risk of intestinal necrosis 1

Long-Term Management

For chronic hyperkalemia management:

• Low-dose daily SPS has been shown to be effective for secondary prevention of hyperkalemia in patients on RAAS inhibitors 6, 7
• Consider newer K+-binding agents (patiromer or sodium zirconium cyclosilicate) which may have better safety profiles 2
• Regular monitoring of electrolytes is essential 5