A 53-year-old man with multiple myeloma is hospitalized after 2 days of polyuria, polydipsia, and increasing confusion. Laboratory tests show an elevated serum $\left[\mathrm{Ca}^{2+}\right]$ of $15 \mathrm{mg} / \mathrm{dL}$, and treatment is initiated to decrease it. The patient's serum osmolarity is $310 \mathrm{mOsm} / \mathrm{L}$.
-The treatment drug is administered in error and produces a further increase in the patient's serum $\left[\mathrm{Ca}^{2+}\right]$. That drug is

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[Chapter 5 , VI C]. Thiazide diuretics would be contraindicated in a patient with severe hypercalcemia because these drugs cause increased $\mathrm{Ca}^{2+}$ reabsorption in the renal distal tubule. On the other hand, loop diuretics inhibit $\mathrm{Ca}^{2+}$ and $\mathrm{Na}^{+}$reabsorption and produce calciuresis. When given with fluid replacement, loop diuretics can effectively and rapidly lower the serum $\left[\mathrm{Ca}^{2+}\right]$. Calcitonin, mithramycin, and etidronate disodium inhibit bone resorption and, as a result, decrease serum $\left[\mathrm{Ca}^{2+}\right]$.

A 53-Year-Old Man with Multiple Myeloma Is Hospitalized After 2 [Ca2+]\left[\mathrm{Ca}^{2+}\right][Ca2+]

A 53-Year-Old Man with Multiple Myeloma Is Hospitalized After 2 $\left[\mathrm{Ca}^{2+}\right]$