Pharmacology · Potassium binders
Sodium polystyrene sulfonate !
A resin taken by mouth or enema that swaps sodium for potassium in the colon. It lowers high potassium slowly.
Updated 2026-11-01
Mechanism of action
Sodium polystyrene sulfonate is a cation-exchange resin that is not absorbed. As it passes along the intestine, mainly in the colon, it releases sodium and takes up potassium, which is then lost in the stool. It is not fully selective, so it also binds some calcium and magnesium.
- The resin reaches the colon unabsorbed
- It releases sodium and binds potassium
- Bound potassium leaves in the stool
- Serum potassium falls over hours to days
Pharmacokinetics
- Absorption
- Not absorbed
- Elimination
- Leaves in the stool with the bound potassium
- Onset and duration
- Lowering of potassium takes hours to days
Indications
- Hyperkalaemia that is not immediately life-threatening, for example in kidney disease Chronic kidney disease →
Adverse effects
Common
- Constipation and faecal impaction
- Nausea, vomiting and loss of appetite
- Diarrhoea
- Low magnesium and calcium
Contraindications
- Obstructive bowel disease
- Hypersensitivity to polystyrene sulfonate resins
- Newborns with reduced gut motility (and the oral route in any newborn)
Key interactions
- Sorbitol
- More risk of intestinal necrosis; the combination is not recommended
- Other oral medicines (e.g. lithium, levothyroxine)
- The resin binds them; doses are separated by several hours
- Antacids or laxatives containing magnesium or aluminium
- Less potassium exchange and risk of metabolic alkalosis
What is monitored
- Serum potassium
- Calcium and magnesium
- Bowel movements and abdominal pain
- Sodium and signs of fluid overload
Nursing care
- Check the potassium before each dose; report ECG changes, because this resin is too slow for an emergency.
- Separate other oral medicines from the resin by the interval in the local protocol.
- Watch bowel function: report constipation, abdominal pain, distension or bleeding.
- Give with the patient sitting upright; take care in patients with a weak gag reflex, who can aspirate the powder.
- Watch for oedema and breathlessness in heart failure (sodium load).
Pregnancy and breastfeeding
Not absorbed, so the fetus is not exposed directly; electrolyte changes in the mother are the concern.
Test yourself
Think of the answer, then tap the question to see it.
Why is sodium polystyrene sulfonate not used alone in life-threatening hyperkalaemia?
Its onset is delayed: lowering potassium takes hours to days, so faster treatments come first.
Which combination with sodium polystyrene sulfonate raises the risk of intestinal necrosis?
Sorbitol.
Why are other oral drugs separated in time from the resin?
The resin binds many drugs in the gut, such as lithium and levothyroxine, and lowers their absorption.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - SODIUM POLYSTYRENE SULFONATE powder, for suspension (DailyMed (U.S. National Library of Medicine), 2026); Sodium Polystyrene Sulfonate: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2017); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.