Individuals in multiple countries are being warning about potentially life-threatening health risks associated with low calcium levels that may be caused by side effects of the bone drugs Xgeva and Prolia. However, it does not appear that similar information is being provided to physicians or patients in the United States.
Amgen, the makers of Xgeva and Prolia, recently warned drug regulators in the U.K. about cases of severe hypocalcemia that have occurred among some patients, causing severe injuries and death.
In a statement released last month by the U.K.’s Medicines and Healthcare products Regulatory Agency (MHRA), the British equivalent of the FDA warned doctors that they should carefully monitor calcium levels in patients taking the drugs.
A similar warning was sent to Canadian health officials in a “public communication” letter (PDF) sent by Amgen on May 31, 2012.
According to the consumer advocacy group Public Citizen, no such warnings have been made public in the United States and the FDA has not warned U.S. physicians about the importance of monitoring calcium levels for users of Xgeva and Prolia.
Xgeva (denosumab) is approved in the U.S. to treat loss of bone density in patients suffering from cancer that has spread to the bones. A lower dose version, Prolia, is used as a treatment for osteoporosis in patients who do not have cancer.
In the latest issue of Public Citizen’s Worst Pills, Best Pills newsletter (subscription), the group is urging individuals using the medications for either cancer or osteoporosis to contact their health care providers immediately if they experience any symptoms of hypocalcemia, or low blood calcium, which could include confusion, muscle spasms, twitching or cramping, or irregularity of the heart rhythm.
Amgen’s warnings provided outside the U.S. indicate that the drugs may lower calcium levels in the blood to dangerous levels, especially in patients with kidney problems. Deaths have occurred among patients being given Xgeva, which has 120 mg of the active ingredient, but not among users of Prolia, which has only 60 mg of the active ingredient.
While most incidents appear to occur within the first six months of treatment, Amgen and foreign drug regulators have indicated that side effects of Xgeva and Prolia may strike at any time during treatment.
In April, the FDA rejected a request by Amgen to approve Xgeva for the treatment of men with prostate cancer that had not spread to their bones. The FDA’s advisory committee said clinical evidence did not show a significant enough benefit for patients to take on the risks of the drug’s side effects. The FDA’s drug reviewers agreed.