Calcium acetate with magnesium carbonate

How it works

Both calcium and magnesium salts bind dietary phosphate in the gut to form non-absorbable complexes, reducing phosphate absorption while lowering the overall calcium load compared with calcium-only binders.

Prescribing in practice

• Take with meals; the magnesium component can cause hypermagnesaemia and diarrhoea, so monitor magnesium and watch for loose stools in patients with reduced renal magnesium clearance.
• Combining calcium with magnesium reduces the elemental calcium dose for a given phosphate-binding effect, which may limit hypercalcaemia and calcium-related vascular calcification.
• Separate from oral iron, levothyroxine, bisphosphonates and certain antibiotics, whose absorption both cations reduce.

Monitoring

Monitor serum phosphate, calcium and magnesium regularly, adjusting the dose to control phosphate while avoiding hypercalcaemia or hypermagnesaemia.

Counselling the patient

• Take with food so it can bind the phosphate in your meal.
• Report persistent diarrhoea, muscle weakness or drowsiness, which may indicate high magnesium.
• Keep other calcium or magnesium-containing products separate unless advised.

Evidence & guidelines

Combined calcium-magnesium binders are an established phosphate-binding option in CKD-MBD management, offering effective phosphate control with a lower calcium burden than calcium-only binders.