Calcium polystyrene sulfonate

How it works

In the gut the resin exchanges calcium ions for potassium ions, which are then bound to the resin and eliminated in the faeces, lowering total body potassium.

Prescribing in practice

• Avoid in obstruction or reduced gut motility and do not give with sorbitol, as the combination has been associated with intestinal necrosis; it is not appropriate for life-threatening hyperkalaemia, which needs emergency treatment.
• It releases calcium and so can cause hypercalcaemia; the calcium form is often preferred over the sodium form where sodium load must be limited.
• Onset is slow over hours, so it is for ongoing potassium control rather than acute emergencies; separate from other oral medicines to avoid binding them.

Monitoring

Monitor serum potassium and calcium during treatment, stopping or reducing therapy once potassium normalises to avoid hypokalaemia.

Counselling the patient

• This medicine lowers potassium gradually and is not a treatment for sudden severe high potassium.
• Report constipation, severe abdominal pain or vomiting promptly.
• Take it separated from your other tablets to keep them working.

Evidence & guidelines

MHRA advice warns against co-administration of polystyrene sulfonate resins with sorbitol owing to the risk of gastrointestinal injury, and these resins remain established options for chronic hyperkalaemia.