Symptomatic hypocalcemia with oral clodronate

We present a patient with prostate cancer who developed symptomatic hypocalcemia while taking oral clodronate for painful bony metastases. He had a past history of a bowel resection for Crohn's disease, and, although he was normocalcemic prior to taking clodronate, it is likely that the surgery had caused mild hyperparathyroidism. The addition of clodronate prevented the chronic osteolysis of bony metastases, which would have helped maintain normocalcemia. The case was complicated by hypomagnesemia and hypokalemia resulting from diarrhea. Hypomagnesemia is a cause of refractory hypocalcemia and hypokalemia. This case illustrates two important points. First, care must be taken with bisphosphonates in patients with a previous bowel resection. Second, magnesium plays a key role in the metabolism of both calcium and potassium, and must be considered in the evaluation of the hypocalcemic patient.