U.S. regulators have never inspected the Chinese plant that makes Baxter International's heparin, regulators disclosed a day after Baxter halted sales of some versions after four patients died and hundreds became ill…Baxter…said it has inspected the facility within the last six months…Baxter spokeswoman Erin Gardiner said that company, which it would not name for proprietary reasons, has been making heparin for more than 30 years…The drug generates about $29 million in annual revenue for Baxter, less than 1 percent of the company's total revenue, Gardiner said.