In the midst of bad news from its painkiller Vioxx, Merck & Co. now has to face similar fallout from its osteoporosis drug Fosamax. Fosamax, prescribed to treat osteoporosis, may have caused the jaw of a Floridian woman to rot. Officials originally believed osteonecrosis, defined as a rotting jaw, was confined to specific chemotherapy drugs. Fosamax and the chemotherapy treatments are in the same class of drugs. In 2004, the FDA learned Fosamax and similar drugs may cause osteonecrosis. Yet in spite of this knowledge, Merck failed and refused to change its label warning.