After recent medical indications that the diet drug combination fenfluramine and phentermine (fen-phen) may damage heart valves, diet centers have begun to rethink their prescription of the popular drugs. The findings, by doctors at the Mayo Clinic, have already prompted the U.S. Food and Drug Administration to send warning letters to thousands of doctors. Now, Jenny Craig Inc, a diet center chain, has recommended that its doctors stop prescribing the pill combination. Another diet center chain, Nutri-System Inc., has said it is reviewing its position with regards to the pills. C. Joseph LaBonte the president and CEO of Jenny Craig Inc., commented, “In light of the Mayo Clinic datawe are advising the independently contracted physicians in our centers that they not prescribe fen-phen until its long-term safety and efficacy is validated.” The company is continuing to offer the drug Redux, which has also been linked to other potentially dangerous side-effects.