Lessons of the month: Over-the-counter antacids causing hypercalcaemia: The emergence of calcium-alkali syndrome.

We present the case of a woman who was found to have severe hypercalcaemia, staghorn calculus formation and renal impairment from the long-standing ingestion of calcium carbonate antacids from a supermarket outlet. The dosage was reported to be approximately 1,800 mg of elemental calcium each day which would constitute only a marginal increase on the recommended intake for daily elemental calcium. Furthermore, she was concomitantly taking a prescribed anti-hypertensive medication that may have exacerbated the hypercalcaemia and subsequent renal calcification. While calcium-alkali syndrome is well documented, it can be overlooked by clinicians as the predominant cause of hypercalcaemia, especially if a thorough drug history is not actively sought. This is particularly important as calcium carbonate products are increasingly being purchased as over-the-counter remedies for dyspepsia management as well as osteoporosis prevention. Explicit product labelling regarding limiting duration usage, potential drug interactions and risk of calcification is therefore recommended. © Royal College of Physicians 2020. All rights reserved.