Case Report Severe Hypocalcemia due to Denosumab in Metastatic Prostate Cancer Mohammed Muqeet Adnan, 1 Usman Bhutta, 1,2 Tanzeel Iqbal, 1 Sufyan AbdulMujeeb, 3 Lukas Haragsim, 2 and Syed Amer 4 1 Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73117, USA 2 Department of Nephrology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73117, USA 3 University of Illinois at Chicago, Chicago, IL 60607, USA 4 Department of Internal Medicine, Mayo Clinic Hospital, Phoenix, AZ 85054, USA Correspondence should be addressed to Mohammed Muqeet Adnan; mohammedabdul-muqeetadnan@ouhsc.edu Received 15 March 2014; Revised 1 June 2014; Accepted 2 June 2014; Published 26 June 2014 Academic Editor: Yoshihide Fujigaki Copyright © 2014 Mohammed Muqeet Adnan et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Denosumab is a monoclonal antibody used for prevention of skeletal-related events (SREs) in patients with bone metastases from solid tumors. Hypocalcemia is a rare and dangerous side efect of the drug Denosumab. We present a case of a patient with metastatic prostate cancer who developed severe hypocalcemia afer the administration of the drug. Te patient’s vitamin D levels were low when checked afer administration of the drug, which likely predisposed him to the development of hypocalcemia. He was placed on high doses of oral and intravenous (IV) calcium and vitamin D without any appreciable response in the serum calcium level. His ionized calcium remained below 0.71 mmol/L despite very high doses of oral and IV calcium supplements. During the hospital course, he developed hydronephrosis from the spread of a tumor and did not want to undergo percutaneous nephrostomy tube placement; therefore, it was decided to dialyse him for acute renal failure and to correct his hypocalcemia. Checking calcium and vitamin D levels prior to the administration of Denosumab is vital in preventing hypocalcemia. If hypocalcemia is severe and not responsive to high doses of vitamin D, oral and IV calcium, then hemodialysis with a high calcium bath can correct this electrolyte abnormality. 1. Case Report A 45-year-old gentleman with a three-year history of meta- static (bone, liver, and lymph nodes) prostate cancer and hypertension presented to the hospital with worsening leg swelling and hematuria. He had been treated with androgen deprivation therapy in the past, along with three doses of zoledronic acid for bone metastases. Te bone pain was not controlled with the above regimen and it was decided to switch him to Denosumab. He received the dose approxi- mately 13 days prior to hospitalization. Vitals at admission were signifcant for a blood pressure (BP) of 160/90 mmHg. Pertinent fndings on physical examination were the presence of bilateral lower extremity edema and negative Chvostek and Trousseau’s signs. Te electrocardiogram showed a prolonged QT interval. Laboratory studies on admission revealed sodium of 135 mEq/L, potassium of 4.9 mEq/L, chloride of 105 mEq/L, bicarbonate of 23 mEq/L, blood urea nitrogen (BUN) of 22 mg/dL, creatinine of 1.34 mg/dL, glu- cose of 133 mg/dL, and calcium of 4.5 mg/dL, with albumin being 2.5 g/dL at admission. Phosphorus level was 6.1 mg/dL. Te ionized calcium level at admission was 0.58 mmol/L. Laboratory studies done 13 days prior, when the drug was given, showed serum calcium of 8.4 mg/dL with an albumin of 2.9 g/dL. His vitamin D levels had not been checked prior to the administration of Denosumab. Afer admission to the hospital, his vitamin D 25-OH level was low at 12.1 ng/mL and vitamin D 1,25 dihydroxy level was high at 95.4 pg/mL. His initial PTH level was high at 440.7 pg/mL. He was started on 50,000 IU of ergocalciferol every 7 days, 2mcg of calcitriol twice daily, and high doses of IV and oral calcium supplementation. Over the next 16 days, the patient Hindawi Publishing Corporation Case Reports in Nephrology Volume 2014, Article ID 565393, 3 pages http://dx.doi.org/10.1155/2014/565393