Final answer:
Redux and Pondimin, also known as fen-phen, were recalled because they caused heart valve problems and Primary Pulmonary Hypertension, leading to concerns about the drug's safety.
Step-by-step explanation:
The weight loss drugs Redux and Pondimin, which were commonly referred to as fen-phen, were recalled after FDA approval and widespread use because they were found to cause serious heart valve problems. These issues included heart valve damage and a rare but potentially fatal condition known as Primary Pulmonary Hypertension (PPH), prompting serious concern over the drug's safety. This led to a re-evaluation of the risks versus benefits of the drug, resulting in its withdrawal from the market.