Fen-Phen May Cause Damage To Heart Valves. An Idaho woman who used the now-banned diet drug, fen-phen, had to have three of four heart valves replaced last week. According to her doctor, her use of fen-phen more than two decades ago caused damage to the valves that was beyond repair. “Unbelievable to think that my valves had just … [Read more...] about Woman’s Damaged Valves Blamed on Fen-Phen