A 68-year-old woman with osteoporosis on denosumab develops muscle cramps and tingling; which adverse effect is most likely?

• A. Hypocalcaemia
• B. Hypercalcaemia
• C. Hyponatremia
• D. Hypermagnesemia

Answer: (A)

Muscle cramps and tingling in a patient on denosumab point to a drop in serum calcium. Denosumab blocks RANKL, which reduces the formation and activity of osteoclasts, leading to less bone resorption and consequently less calcium released from bone into the bloodstream. In people who may already have low calcium intake or vitamin D deficiency (common in older adults), this can tip calcium levels into hypocalcemia. Hypocalcemia explains the neuromuscular symptoms like cramps and paresthesias.

Hypercalcemia would be unlikely here because the drug’s effect is to lower, not raise, calcium levels. Hyponatremia and hypermagnesemia are not typical consequences of denosumab therapy. To prevent this, calcium and vitamin D status should be optimized before and during treatment, with monitoring and treatment for symptomatic hypocalcemia if it occurs.