Ciprofloxacin, sold by Bayer under the brand name Cipro, is an antibiotic. Cipro was the most widely prescribed quinolone in 1995, with U.S. sales in 1996 of 0 million.48 Bayer and firstfiler Barr49 reached agreement in January 1997.50 Bayer paid Barr 8 million by December 2003: .1 million initially, followed by quarterly payments. Although the agreement provided for private label sales along the lines of the tamoxifen agreement, this provision was not implemented. Bayer exercised its option under the agreement to pay cash instead. As with the tamoxifen agreement, Barr retained potential entitlement to the exclusivity period, without fear of losing it by losing a patent suit. Barr initially changed its Paragraph IV certification to Paragraph III, thereby certifying that it would wait to enter until patent expiration.