Introduction
Kayexalate (sodium polystyrene sulfonate) is a cation-exchange resin used primarily for the treatment of hyperkalemia (elevated serum potassium levels). First approved by the FDA in 1975, it remains an important therapeutic option for managing potassium excess, particularly in patients with renal impairment. Kayexalate works by binding potassium in the gastrointestinal tract, facilitating its elimination from the body.
Mechanism of Action
Kayexalate acts as a sodium-potassium exchange resin in the gastrointestinal tract. The resin contains sodium ions attached to a polystyrene polymer. When administered, the resin releases sodium ions in exchange for other cations, primarily potassium, throughout the intestinal lumen. The bound potassium is then excreted in the feces, thereby reducing serum potassium levels. Each gram of Kayexalate can bind approximately 1 mEq of potassium while releasing 1-2 mEq of sodium.
Indications
- Treatment of hyperkalemia
- Adjunctive therapy in management of potassium overload
- Particularly useful in patients with renal impairment who cannot effectively eliminate potassium
Dosage and Administration
Standard adult dosage: 15-30 grams orally 1-4 times daily, or 30-50 grams as a retention enema every 6 hours Oral administration:- Mix powder with water or syrup (20-100 mL per dose)
- Preferably administer with food to minimize gastrointestinal upset
- Should not be heated
- Prepare as a suspension in 100 mL of aqueous vehicle
- Administer as retention enema, retained for 30-60 minutes
- Follow with cleansing enema
- Renal impairment: No dosage adjustment required
- Hepatic impairment: Use with caution due to sodium load
- Pediatrics: 1 gram/kg body weight per dose orally or rectally
Pharmacokinetics
Absorption: Not absorbed systemically; acts locally in the GI tract Distribution: Confined to gastrointestinal lumen Metabolism: Not metabolized Elimination: Excreted unchanged in feces along with bound potassium Onset of action: 2-24 hours after oral administration; more rapid with rectal administration Duration of effect: 4-6 hoursContraindications
- Hypersensitivity to sodium polystyrene sulfonate or any component
- Hypokalemia
- Obstructive bowel disease
- Paralytic ileus
- Neonates with reduced gut motility
- Patients on sodium restriction (relative contraindication)
Warnings and Precautions
Black Box Warning: Risk of intestinal necrosis, which may be fatal. This serious adverse event has been reported with concomitant use of sorbitol.- Use with extreme caution in patients with constipation, bowel obstruction, or inflammatory bowel disease
- Monitor for signs of intestinal necrosis (abdominal pain, distension, nausea, vomiting)
- Caution in patients with heart failure, hypertension, or edema due to sodium load
- Risk of hypokalemia with prolonged use
- May cause hypocalcemia and hypomagnesemia
- Elderly patients may be more susceptible to complications
Drug Interactions
- Antacids containing magnesium or calcium: May decrease potassium-binding capacity
- Lithium: Kayexalate may decrease lithium absorption
- Thyroid medications: May decrease absorption of levothyroxine
- Oral medications: May bind other orally administered drugs; administer other medications at least 3 hours before or 3 hours after Kayexalate
- Sorbitol-containing products: Increased risk of intestinal necrosis (contraindicated)
Adverse Effects
Common (≥1%):- Constipation (most frequent)
- nausea
- vomiting
- diarrhea
- anorexia
- Intestinal necrosis (rare but potentially fatal)
- Hypokalemia
- Hypocalcemia
- Hypomagnesemia
- Sodium overload leading to edema, hypertension, or heart failure
- Electrolyte imbalances
- Fecal impaction
Monitoring Parameters
- Serum potassium levels (before and during therapy)
- Serum sodium, calcium, and magnesium levels
- ECG changes associated with hyper/hypokalemia
- Bowel function and abdominal exam
- Fluid status and body weight
- Signs of intestinal necrosis (abdominal pain, distension)
- In patients with cardiac or renal impairment: blood