PPI Hypomagnesaemia — RACP Adult Medicine MCQ

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ModerateClinical PharmacologyPPI HypomagnesaemiaRACP Adult Medicine

A 72-year-old woman on long-term proton pump inhibitor (esomeprazole) for GORD develops hypomagnesaemia (Mg 0.4 mmol/L) and secondary hypocalcaemia despite adequate calcium supplementation. What is the mechanism?

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Correct answer: E — PPI-induced impaired intestinal magnesium absorption via TRPM6/7 channels

PPIs can cause hypomagnesaemia through impaired intestinal magnesium absorption via inhibition of TRPM6/7 channels in the GI tract. This is a class effect of all PPIs and typically occurs with prolonged use (>3 months, often >1 year). Hypomagnesaemia causes secondary hypocalcaemia (magnesium is required for PTH secretion and action) and hypokalaemia (renal potassium wasting). Management involves magnesium supplementation (IV for severe cases) and consideration of PPI cessation or substitution with an H2-receptor antagonist if possible. The TGA has issued safety communications about this risk.

Reference: AMH – 2025 – PPI Adverse Effects; TGA – 2024 – PPI Hypomagnesaemia Safety Alert