SAT-756 - Identifying Risk Factors for Hypocalcemia Following Zoledronic Acid Therapy

Background/

Objectives: Zoledronic acid is a bisphosphonate that reduces skeletal-related events by inhibiting osteoclast activity and is prescribed for patients with osteoporosis or osteopenia. Hypocalcemia is a common side effect, with severe cases occurring even after calcium and vitamin D supplementation. Our goal is to identify vulnerable populations with increased risk of developing hypocalcemia following zoledronic acid administration in order to improve supplementation and monitoring guidelines.

Methods: This study is a retrospective chart review. Independent variables included demographic characteristics (sex, race, and ethnicity) as well as presence of Chronic Kidney Disease (CKD) stage 3 or higher as defined by ICD-10 code N18.3-5. The dependent variables were the occurrence of standard hypocalcemia (serum Ca < 8.4 mg/dL) and severe hypocalcemia (Ca < 7.0 mg/dL). Our analysis encompassed calcium measurements obtained within six months of zoledronic acid administration from 2018 to now. Data was extracted from Epic SlicerDicer and analyzed using a multiple logistic regression model.

Results: Our population consisted of 2760 patients from ages 18-90 using zoledronic acid for osteopenia or osteoporosis. There were 131 patients with standard hypocalcemia, and 10 with severe. After controlling for race and ethnicity, males had increased odds of developing both hypocalcemia (OR=3.08, 95% CI [2.03-4.68], p< 0.001) and severe hypocalcemia (OR= 5.14, 95% CI [1.40-18.88], p=0.014) compared to females. Asian, African-American, and Other race was not significantly associated with increased odds of standard hypocalcemia compared to Caucasian race, and neither was Hispanic compared to non-Hispanic ethnicity. African-American race demonstrated 10.10 increased odds of severe hypocalcemia compared to Caucasian race (95% CI [2.48-41.08], p=0.001), but the population only consisted of 7 Caucasian and 3 African-American patients. The impact of Asian race and Hispanic ethnicity on severe hypocalcemia was inconclusive due to lack of data. Patients with CKD stage 3 or higher had 4.38 increased odds of hypocalcemia compared to those with CKD stage 1, 2, or no CKD (95% CI [2.59-7.40], p< 0.001). CKD stage 3 or higher was not significantly associated with increased odds of severe hypocalcemia, although the population of interest was small (n=10).

Conclusions: We identified male sex as a significant risk factor for hypocalcemia and severe hypocalcemia in correlation with previous studies on analogous medication like denosumab, which can be linked to gender-based dimorphism of osteoclast number and function. Moreover, patients with moderate to severe CKD are at higher risk for hypocalcemia.

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