Calcium Acetate 667mg (PhosEx)

How it works

Calcium binds dietary phosphate in the gut to form insoluble calcium phosphate, which is excreted in the faeces, thereby reducing phosphate absorption.

Prescribing in practice

• Must be taken with food (immediately before or with meals) to bind dietary phosphate; taken away from food it provides little phosphate binding and risks hypercalcaemia.
• Provides less elemental calcium per unit of phosphate bound than calcium carbonate, but the total calcium load still contributes to vascular calcification risk.
• Separate administration from oral iron, levothyroxine and many antibiotics (e.g. tetracyclines, quinolones), whose absorption it reduces.

Monitoring

Monitor serum calcium, phosphate and the calcium-phosphate product, with periodic parathyroid hormone review, adjusting therapy to avoid hypercalcaemia.

Counselling the patient

• Take each dose with meals to mop up the phosphate in your food.
• Report symptoms of high calcium such as nausea, constipation, thirst or confusion.
• Do not take indigestion remedies or other calcium supplements without advice.

Evidence & guidelines

Phosphate binders are recommended in CKD-mineral and bone disorder guidance (NICE/KDIGO) to control hyperphosphataemia, with calcium-based binders used cautiously because of calcium loading.