A Food and Drug Administration panel has has voted to improve the labeling of a class of osteoporosis drugs known as bisphosphonates.

The drugs have been linked to high cases of thigh fractures and other side effects particularly when taken over longer time periods.

The panel suggests that manufacturers improve drug labeling which increases "cautionary language" surrounding taking the drugs particularly as the evidence surrounding them are still being fully understood.

"I don't think we have enough data to restrict anything at this point," said Dr. Maria Suarez-Almazor, professor at the University of Texas MD Anderson Cancer Center, according to Reuters. The response came after being asked whether bisphosphonates should have imposed drug holidays.

The bisphosphonate drugs which the members of the advisory committee have imposed labeling on include Fosamax by Merck whose sales peaked at $3.2 billion in 2005.

Worldwide, alternatives to Fosamax - Reclast, a once a year infusion - and Boniva by Swiss Pharmaceutical Roche made between $7.6 billion and $8.8 billion in 2007, with revenues diminishing as the drug becomes generic.

According to an FDA statement issued yesterday, "a drug holiday" may be used, though there is no evidence to warrant it.