In severe hypercalcemia, which medication provides a rapid but temporary reduction in calcium levels?

• A. Calcitonin
• B. Bisphosphonates
• C. Furosemide
• D. Dialysis

Answer: (A)

Calcitonin provides a quick drop in calcium by opposing PTH’s effects: it inhibits osteoclast-driven bone resorption and promotes calcium excretion by the kidneys. This results in a rapid reduction in serum calcium within hours, making it the fastest option available. However, its effect wanes quickly due to tachyphylaxis, usually within 24 to 48 hours, so the calcium-lowering action is temporary. Because of this, calcitonin is best used as a bridge to longer-acting measures that provide sustained lowering, such as intravenous fluids to promote calciuresis plus bisphosphonates (like pamidronate or zoledronic acid) or other agents, depending on the clinical scenario. Dialysis can rapidly reduce calcium but is reserved for patients with renal failure or refractory cases and isn’t a medication.