What is the recommended pediatric dose of sodium polystyrene sulfonate (Kayexalate) for treating non‑life‑threatening hyperkalaemia in children?

Pediatric Dosing of Sodium Polystyrene Sulfonate (K-bind/Kayexalate) for Non-Life-Threatening Hyperkalemia

For non-life-threatening hyperkalemia in children, administer sodium polystyrene sulfonate (SPS) at 1 g/kg orally every 6 hours as needed, or 1 g/kg rectally every 6 hours as needed, with a maximum single dose of 15 g orally (60 mL) or 50 g rectally. 1

Critical Pre-Administration Safety Considerations

Neonatal Population – Avoid Sorbitol Formulations

• Never use commercially available liquid SPS preparations in neonates due to hyperosmolar sorbitol content, which can cause intestinal hemorrhage (hematochezia), particularly in extremely preterm neonates. 1
• Hospital pharmacies must prepare sorbitol-free formulations for this population 1
• Extremely low birth weight (ELBW) infants receiving rectal Kayexalate are at highest risk for gastrointestinal complications 1

Hypernatremia Risk in Preterm Infants

• ELBW infants (<1000 g) treated with SPS can develop serious hypernatremia, as each 15 g dose delivers approximately 1500 mg sodium 1, 2
• Monitor serum sodium closely in preterm infants, as this complication has been documented but may be underrecognized 2

Route Selection and Practical Considerations

Oral Administration (Preferred Route)

• 91% of pediatric doses are administered orally in clinical practice, making this the preferred route when the gastrointestinal tract is functional 3
• Oral route is more effective than rectal administration for achieving target potassium reduction 3

Rectal Administration

• Reserve for patients unable to tolerate oral intake or with non-functioning GI tract 1
• Avoid rectal route in neutropenic patients due to infection risk 1
• Patients requiring rectal SPS are more likely to need additional interventions for hyperkalemia management 3

Expected Efficacy and Timing

Onset and Duration

• SPS has a variable onset of action taking several hours to days, making it unsuitable for emergency treatment of life-threatening hyperkalemia 1, 4, 5
• In pediatric studies, the nadir potassium concentration occurred at a mean of 16.7 ± 14.7 hours post-dose 3
• Mean potassium reduction from peak (6.5 ± 0.77 mmol/L) to nadir (4.7 ± 1.2 mEq/L) represents approximately 28% decrease 3

When SPS May Be Insufficient as Monotherapy

• SPS is not appropriate as a first single-line agent in patients with severe acute hyperkalemia requiring >25% reduction in serum potassium or those at high risk for cardiac arrhythmias 3
• 43% of pediatric patients required at least one additional intervention within 48 hours after initial SPS dose 3
• Patients with higher baseline potassium levels and lower body weight are more likely to require additional interventions 3

Life-Threatening Hyperkalemia – Use Rapid-Acting Agents First

For life-threatening hyperkalemia (K+ >6.5 mEq/L or ECG changes), immediately administer rapid-acting treatments before considering SPS:

• IV calcium gluconate to stabilize cardiac membranes 1, 5
• Insulin (0.1 U/kg IV) with glucose infusion (25% dextrose 2 mL/kg) to shift potassium intracellularly 1
• Sodium bicarbonate (1-2 mEq/kg IV push) for transcellular shift 1
• SPS may be added as adjunctive therapy after these immediate interventions 5

Monitoring and Adverse Events

Gastrointestinal Complications

• 15% of pediatric patients experience documented gastrointestinal adverse events with SPS 3
• Serious complications include intestinal necrosis, perforation, ischemic colitis, and bleeding, with an overall mortality rate of 33% among affected patients 1, 5

Electrolyte Monitoring

• SPS is nonselective and binds calcium and magnesium in addition to potassium, potentially causing hypocalcemia and hypomagnesemia 1, 4
• Monitor serum potassium, sodium, calcium, and magnesium during therapy 4
• Verify potassium levels immediately with a second sample to rule out fictitious hyperkalemia from hemolysis 1

Alternative Approaches for Chronic Management

Newer Potassium Binders (When Available)

• For chronic hyperkalemia management, patiromer and sodium zirconium cyclosilicate are preferred over SPS due to superior safety profiles and more predictable onset of action 4, 5
• These agents should be considered especially in patients who don't respond adequately to SPS 4

Insulin-Glucose Therapy for VLBW Infants

• In very low birth weight infants with non-oliguric hyperkalemia, continuous regular insulin infusion (ratio 10-15 g glucose per 1 unit insulin, maintaining glucose infusion rate ≥6 mg/kg/min) is more effective than Kayexalate, with shorter duration of hyperkalemia (26.4 vs 38.6 hours) and lower incidence of intraventricular hemorrhage (15% vs 50%) 6

Formula Pretreatment for Infants

• For infants at risk of hyperkalemia, pretreatment of infant formula with SPS (1 g/mEq of K+) can reduce potassium content by 4.5-fold, though this also increases sodium content by 3.8-fold 7
• Preparing formula with deionized water reduces potassium by 30% compared to ready-to-feed formula and may be more practical 7
• Contact time of 1 or 24 hours does not impact potassium removal; effectiveness plateaus beyond 20 mL SPS addition 8

Common Pitfalls to Avoid

• Never rely on SPS alone for emergency hyperkalemia management – its delayed onset makes it inappropriate for acute, life-threatening situations 4, 5
• Never use sorbitol-containing preparations in neonates – risk of intestinal hemorrhage outweighs benefits 1
• Avoid chronic SPS use – serious GI complications including bowel necrosis make it unsuitable for long-term management 5
• Monitor for hypernatremia in ELBW infants, as this serious complication is documented but may be overlooked 2
• Recognize that rectal administration is associated with higher failure rates requiring additional interventions 3