Usage
Polystyrene sulfonate is prescribed to treat hyperkalemia, a condition characterized by elevated potassium levels in the blood. It is classified as a potassium-removing resin, specifically a cation-exchange resin. It works by exchanging sodium ions for potassium ions in the digestive tract, thereby reducing the absorption of potassium and promoting its excretion in the feces.
Alternate Names
- Sodium polystyrene sulfonate (SPS)
- Calcium polystyrene sulfonate
- Kayexalate
- Kionex
- Resonium A
- Calcium Resonium
- Sorbisterit
- Resikali
How It Works
Pharmacodynamics: Polystyrene sulfonate works primarily in the large intestine. The resin is not absorbed systemically. Its action is localized to the lumen of the gut. It exchanges sodium (or calcium) ions for potassium ions. This binding of potassium prevents its absorption into the bloodstream, facilitating its elimination through the feces. It does not directly affect serum potassium levels. Instead, it reduces the net potassium load by preventing further absorption from dietary intake. It is important to monitor other electrolyte levels (calcium, magnesium) as polystyrene sulfonate can also bind to them. The effects of polystyrene sulfonate are typically seen within hours to days.
Pharmacokinetics: Polystyrene sulfonate is not absorbed systemically following oral or rectal administration. It remains within the gastrointestinal tract and is excreted in the feces. Thus, there are no conventional pharmacokinetic parameters like absorption, distribution, metabolism, or elimination half-life.
Mode of Action: Polystyrene sulfonate acts as a cation-exchange resin in the large intestine. The sulfonate groups on the resin bind potassium ions while releasing sodium or calcium ions, preventing potassium absorption. The resin itself is not absorbed, passing through the digestive tract and being eliminated in the stool along with the bound potassium.
Dosage
Standard Dosage
Adults:
- Oral: 15 g (approximately 4 level teaspoons) one to four times daily.
- Rectal: 30-50 g every six hours as a retention enema.
Children:
- Oral: 1 g/kg body weight daily, divided into doses, for acute hyperkalemia. For maintenance, 0.5 g/kg body weight daily, in divided doses. (Oral use is not recommended for infants younger than one month).
- Rectal: 1 g/kg every 2-6 hours as needed, or as directed by the clinician.
Special Cases:
- Elderly Patients: Large doses may increase the risk of fecal impaction. Careful monitoring and dose adjustment are necessary. Rectal administration may be preferable.
- Patients with Renal Impairment: Dose adjustments based on the severity of renal impairment and serum potassium levels are often required. Close monitoring of potassium levels is essential.
- Patients with Hepatic Dysfunction: No specific dose adjustments are typically necessary as the drug is not metabolized by the liver.
- Patients with Comorbid Conditions: Caution is advised for patients with heart failure, severe hypertension, or marked edema due to the sodium content of sodium polystyrene sulfonate. Careful monitoring of fluid and electrolyte balance is needed.
Clinical Use Cases
Dosage adjustments are made according to the individual patient’s needs and clinical setting. There are no specific dosage recommendations for clinical use cases like intubation, surgical procedures, mechanical ventilation, or ICU use. In emergency situations with severe hyperkalemia, other, more rapid-acting treatments are usually preferred, like intravenous calcium, insulin with glucose, or hemodialysis.
Dosage Adjustments
Dose adjustments are needed for renal dysfunction, heart failure, hypertension, and edema. Close monitoring of electrolytes is essential, especially potassium, calcium, and magnesium. For patients with gastroparesis, consider separating polystyrene sulfonate administration from other oral medications by at least 6 hours.
Side Effects
Common Side Effects
- Nausea
- Vomiting
- Diarrhea
- Constipation
- Loss of appetite
Rare but Serious Side Effects
- Intestinal necrosis (rare but potentially fatal)
- Gastrointestinal bleeding or ulceration
- Fecal impaction (especially in children and the elderly)
- Electrolyte imbalances (hypokalemia, hypocalcemia, hypomagnesemia)
- Sodium overload and fluid retention (especially in patients with heart failure or renal impairment)
Long-Term Effects
- Chronic use may lead to persistent constipation, electrolyte abnormalities, or other gastrointestinal complications.
Adverse Drug Reactions (ADR)
- Severe allergic reactions (rare)
- Ischemic colitis and intestinal perforation (rare)
- Severe hypokalemia or other electrolyte disturbances
Contraindications
- Hypersensitivity to polystyrene sulfonate resins
- Hypokalemia
- Obstructive bowel disease
- Neonates with reduced gut motility (oral administration)
- Use with sorbitol in neonates (rectal administration)
Drug Interactions
- Antacids and laxatives containing aluminum or magnesium: May increase the risk of systemic alkalosis or intestinal obstruction.
- Sorbitol: Concurrent use with sorbitol, particularly in enema formulations, has been associated with cases of intestinal necrosis.
- Digitalis glycosides: Polystyrene sulfonate-induced hypokalemia may enhance the toxicity of digitalis.
- Lithium: Polystyrene sulfonate may reduce lithium absorption.
- Levothyroxine: Polystyrene sulfonate may decrease levothyroxine absorption.
- Other orally administered medications: Polystyrene sulfonate can bind to various drugs in the GI tract, potentially reducing their absorption. Separate administration by at least 3 hours, or 6 hours in patients with gastroparesis.
Pregnancy and Breastfeeding
- Pregnancy: Polystyrene sulfonate is not absorbed systemically, so it is not expected to cause fetal harm. However, its use during pregnancy should be limited to cases where the benefits outweigh the risks.
- Breastfeeding: It is unknown whether polystyrene sulfonate is excreted in breast milk. However, due to its lack of systemic absorption, it poses minimal risk to the nursing infant.
Drug Profile Summary
- Mechanism of Action: Cation-exchange resin that binds potassium in the GI tract, preventing its absorption.
- Side Effects: Constipation, diarrhea, nausea, vomiting, loss of appetite. Rarely: intestinal necrosis, fecal impaction, electrolyte imbalances.
- Contraindications: Hypersensitivity, hypokalemia, bowel obstruction, neonates with reduced gut motility.
- Drug Interactions: Antacids/laxatives with aluminum/magnesium, sorbitol, digitalis, lithium, levothyroxine.
- Pregnancy & Breastfeeding: Generally considered safe due to minimal systemic absorption, but use only if clearly needed.
- Dosage: Adults: 15-60g daily divided 1-4 times/day. Children: 1 g/kg/day for acute hyperkalemia; 0.5 g/kg/day for maintenance.
- Monitoring Parameters: Serum potassium, calcium, magnesium levels, and bowel function.
Popular Combinations
Polystyrene sulfonate is not typically used in fixed combinations with other drugs. It may be used in conjunction with other treatments for hyperkalemia, such as intravenous calcium or insulin/glucose, in emergency situations.
Precautions
- General Precautions: Monitor electrolytes, especially potassium. Assess bowel function regularly. Be cautious in patients with congestive heart failure, severe hypertension, or marked edema due to the sodium content.
- Specific Populations: See dosage adjustments for elderly, renal impairment, and other comorbidities. Close monitoring is essential.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Polystyrene Sulfonate?
A: Adults: 15-60 g/day (oral or rectal); Children: 1 g/kg/day (acute), 0.5 g/kg/day (maintenance).
Q2: How does Polystyrene Sulfonate work?
A: It acts as a cation-exchange resin, binding potassium in the gut and promoting its excretion in the feces.
Q3: What are the common side effects of Polystyrene Sulfonate?
A: Constipation, diarrhea, nausea, vomiting, and loss of appetite.
Q4: What are the serious side effects to watch out for?
A: Intestinal necrosis (rare), fecal impaction, severe electrolyte imbalances (hypokalemia, hypomagnesemia, hypocalcemia).
Q5: Who should not take Polystyrene Sulfonate?
A: Patients with hypokalemia, bowel obstruction, hypersensitivity to the drug, and neonates with reduced gut motility (oral).
Q6: Can pregnant or breastfeeding women use this medication?
A: Generally considered safe due to lack of systemic absorption, but should only be used if clearly needed and under medical supervision.
Q7: What are the potential drug interactions with Polystyrene Sulfonate?
A: Antacids/laxatives with aluminum/magnesium, sorbitol, digitalis glycosides, lithium, and levothyroxine. It can also decrease the effectiveness of other oral medications taken concurrently.
Q8: How should Polystyrene Sulfonate be administered?
A: Orally as a powder mixed with water or syrup, or rectally as a retention enema.
Q9: How long does it take for Polystyrene Sulfonate to work?
A: Effects are typically seen within a few hours to days.
Q10: What should I monitor in patients taking Polystyrene Sulfonate?
A: Serum electrolyte levels (potassium, calcium, magnesium), bowel function, and signs of any adverse gastrointestinal effects.
