Prolia and Xgeva Side Effects May Include Heart Rhythm Risks, Australia Warns

Drug regulators in Australia are warning that the bone drugs Prolia and Xgeva, both of which use the active ingredient denosumab and are also available in the United States, could cause users to suffer abnormal heart rhythms linked to lowered calcium levels. 

Australia’s Therapeutic Goods Administration (TGA), part of the nation’s health department, issued a medicines safety update on August 11, indicating that side effects of Prolia and Xgeva may increase the risk of QT prolongation.

The TGA warning came in the wake of an assessment of adverse event reports submitted to Australian regulators. QT prolongation can cause heart rhythm problems such as irregular heartbeats (arrhythmias) which can cause serious health problems or even death.

While both use denosumab as the active ingredient, Prolia is given twice a year for the treatment of osteoporosis. Xgeva is used once a month to prevent skeletal problems in adults diagnosed with metastases from solid tumors.

Australian regulators believe the prolonged QT intervals are a side effect of hypocalcemia, or low calcium serum levels in the blood. Hypocalcemia is already listed on the drugs’ labels as a risk, but the TGA notes that QT Prolongation is not, nor is the label clear that there is a risk of severe levels of hypocalcemia.

The drugs’ product information documents in Australia have been changed. It is unclear whether the labels and product information guides will also be changed in the U.S. or other countries.

Denosumab is a monoclonal antibody that was first approved in June 201o for Amgen, Inc.’s Prolia, and then later approved in November 2010 as Xgeva, again for Amgen. It inhibits the development of osteoclasts, resulting in decreased bone resportion and increased bone density.