Researchers say seizures related to osteoporosis medication are rare, caused by mitigating factors

The potential side effects of zoledronic acid, a prescription medication used to treat or prevent osteoporosis, include seizures, but research has found that these are exceedingly rare and usually the result of unanticipated drug interactions, hypoglycemia or a history of epilepsy.

A report published in the Journal of Clinical Endocrinology and Metabolism related the case studies of three elderly individuals with osteoporosis, all of whom seized after being given injections of the drug as part of a therapeutic regimen to improve bone density.

In each case, doctors determined that mitigating factors appeared to be the cause of the seizure.

Zoledronic acid, also known by the brand name Reclast, is prescribed for osteoporosis in the form of an injection. It is not intended to be used regularly, since the substance, a potent bisphosphonate, has the potential for overdose, according to the National Institutes of Health (NIH).

The agency notes that overdosing on the drug can lead to seizures, though the study's authors said that this was not a factor in any of the cases presented in their report.

To give some idea of how infrequently zoledronic acid may be administered, the NIH notes that women prescribed the drug as a preventative measure against osteoporosis are usually given no more than one shot every two years.

In the study, all three patients were at least 75 years old and had been diagnosed with osteoporosis. Two of them were taking a number of other medications, and the third had undergone a total gastrectomy - or complete removal of the stomach - five years previously.

The team determined that in the latter case, the individual suffered a seizure related to hypoglycemia, not to the injection of zoledronic acid. After recovering, she revealed that she had skipped a meal out of excitement over her "osteoporosis shot."

The other two patients had a history of seizures, and one had had a partial gastrectomy, putting him at risk for hypoglycemia. Both also took a number of medications for epilepsy, hypertension or chronic pain.

Seizures affect about 3 million Americans, according to the Epilepsy Foundation, and the National Osteoporosis Foundation estimates that 10 million people suffer from osteoporosis.