Kayexalate
Kayexalate
Generic Name
Kayexalate
Mechanism
- Sodium‑potassium ion exchange:
*The resin’s sulfonate groups bind sodium ions in the blood‑non‑absorbable gastrointestinal lumen. Once inside the intestinal tract, the resin releases the bound sodium and captures circulating potassium, forming a non‑digestible complex that is excreted unchanged.*
• Limited acid base exchange:
Although primarily a potassium binder, Kayexalate can also exchange hydrogen ions, thereby shifting mild metabolic acidosis toward a more alkaline state, especially in severe renal failure.
Pharmacokinetics
- Absorption: None – the resin is not systemically absorbed.
- Distribution: Local action within the GI tract; no systemic distribution.
- Metabolism: No hepatic metabolism.
- Excretion: Non‑absorbed resin, bound potassium, and liberated sodium are eliminated unchanged in feces.
- Gastro‑intestinal transit: Linear clearance; typical transit time 6–8 h in a healthy colon.
- Bioavailability: 0 % systemic bioavailability; action is strictly local.
Indications
- Acute hyperkalemia (K⁺ > 6 mmol/L) – as an adjunct to dialysis or potassium‑lowering agents.
- Recurrent hyperkalemia in chronic kidney disease – aids in long‑term potassium reduction.
- Hypernatremia – rarely used due to risk of sodium overload; reserved for severe cases when sodium conservation is needed.
- Severe metabolic acidosis – when the acid–base imbalance is linked to chronic renal failure (off‑label).
Contraindications
- Bowel obstruction, ileus, or severe constipation – risk of resin accumulation and perforation.
- Recent gastrointestinal surgery – increased susceptibility to necrosis.
- Severe malnutrition or inflammatory bowel disease (Crohn’s, ulcerative colitis) – higher risk of colonic injury.
- Concurrent use of sorbitol or polyethylene glycol – historically associated with necrosis; sorbitol is now avoided, yet careful monitoring is essential.
- Pregnancy – category C; use only if benefits outweigh risks.
- Lactation – minimal data; prudence advised.
Warnings
• Gastrointestinal necrosis or perforation – rare but life‑threatening, especially in high doses or with sorbitol.
• Electrolyte shifts – over‑cautious use can precipitate hypokalemia; monitor serum potassium closely.
• Hyponatremia – possible if excessive sodium is displaced or if fluid replacement is inadequate.
Dosing
| Setting | Dosage | Administration |
| Acute hyperkalemia (oral) | 15 g (15–30 g total, divided up to four doses) | Powders dissolved in 60–120 mL water; take orally or via nasogastric tube |
| Acute hyperkalemia (phosphate) | up to 30 g total | As above |
| Severe hyperkalemia (repetitive) | 2.5–3.5 g every 4–6 h | Until potassium normal, then taper |
| Chronic hyperkalemia (maintenance) | 15 g daily | 10–15 g in divided doses |
| Hypernatremia | 10 g per liter of feeding | As needed under nephrology supervision |
• Preparation: Mix the powder with water, shake or stir until completely dissolved; use within 1 h.
• Avoid: Mixing with sorbitol or high‑osmolar solutions unless specifically directed by a pharmacist.
Adverse Effects
- Common
- Constipation, diarrhea, or abdominal cramping
- Nausea, vomiting, or dyspepsia
- Taste alterations (resin in the mouth)
- Serious
- Colonic necrosis with potential perforation
- Severe electrolyte disturbances (hypo‑ or hyper‑natremia)
- Allergenic reactions (rare, but anaphylaxis possible)
> Key Takeaway: Regularly monitor stool form and weight; seek immediate care if abdominal pain, distention, or vomiting develops.
Monitoring
| Parameter | Frequency | Target/Alert |
| Serum potassium (K⁺) | Every 4–6 h during acute therapy, daily thereafter | < 5 mmol/L (acute) |
| Serum sodium (Na⁺) | Daily during hypernatremia correction | Normal range (135–145 mmol/L) |
| Renal function (Cr, BUN) | Once weekly if CKD | Stable or improving |
| Electrolytes (Cl⁻, Ca²⁺, Mg²⁺) | Every 4–6 h initially | Within normal limits |
| Hemoglobin/Hematocrit | Once weekly | Stable |
| LFTs | Monthly | No abnormalities |
| Lactate and metabolic panels | As clinically indicated | Acidosis resolution |
| GI assessment | Daily | No signs of obstruction or perforation |
Clinical Pearls
- Resin‑sorbitol association: Historically, many perforation cases trailed from mixing Kayexalate with sorbitol. Modern formulations usually omit sorbitol, but never mix with any high‑osmolar laxatives unless specifically instructed.
- Timing with other potassium‑lowering agents: Use sequentially, not concomitantly with dialysis; the resin’s effect is delayed, so avoid overlapping therapy that may overwhelm the gastrointestinal tract.
- Conservative sodium load: Since the resin releases roughly 1 mol of sodium per 30 g dose, consider supplemental fluid to counter potential hyponatremia, especially in fluid‑restricted patients.
- Monitoring for abdominal pain: A sudden change or severe cramp should prompt imaging to rule out colon necrosis; the decision to discontinue therapy might be required.
- Use in pediatrics: Pediatric dosing is not standardized; weigh the risk–benefit, and opt for smaller, fractionated doses while caring for the risk of constipation.
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• Kayexalate remains a valuable tool in the armamentarium against hyperkalemia, but like all ion‑exchange resins, it demands meticulous attention to dose, patient selection, and vigilant monitoring to avert severe gastrointestinal complications.