In January, Baxter International sent a warning to customers about issues with its Colleague infusion pumps that could cause them to stop pumping and overheat. On Wednesday the company said the FDA classified the announcement as a Class I recall, its most severe warning. The classification applies to problems that can cause "serious adverse health consequences or death."

Public Citizen's Dr. Sidney Wolfe blasted the agency in a letter Thursday for not moving faster.

"Why did it take the FDA 47 days, almost 7 weeks ... to decide that this problem was serious enough to merit being classified as a Class I recall?" Wolfe wrote in a letter to acting FDA Commissioner Dr. Frank Torti.

FDA's classification has limited real-world impact. Baxter's products are not actually being called off the market, but the serious warning is necessary because malfunctions with the devices can be fatal.