The Food and Drug Administration needs an independent drug safety office with the power to order pharmaceutical companies to add warning labels to dangerous medicines, a top U.S. Senate Republican said on Thursday.Senate Finance Committee Chairman Charles Grassley said he was preparing legislation to establish such an office in response to controversies surrounding Merck & Co. Inc’s withdrawn arthritis pill Vioxx and other drugs."We need reforms, both administrative and legislative, to bring greater responsiveness and transparency to the FDA,” Grassley said in remarks prepared for delivery at a Consumer Federation of America conference.The new drug safety office “would have an independent director and the regulatory authority to require label changes,” the Iowa Republican said.