Which of the following drugs is associated with weight loss but has been discontinued?

Fen-Phen, which is a combination of fenfluramine and phentermine, was prescribed for weight loss due to its effectiveness in suppressing appetite. However, it was discontinued because it was associated with serious health risks, including pulmonary hypertension and valvular heart disease. The evidence of these severe side effects prompted health authorities to take action and withdraw the drug from the market.

In contrast, while Adderall can result in weight loss as a side effect due to its stimulant properties, it is primarily used to treat attention deficit hyperactivity disorder (ADHD) and narcolepsy and has not been discontinued for weight management purposes. Prozac, an antidepressant, may also have some weight-related effects, but it is not primarily prescribed for weight loss and remains available. Ativan, used primarily for anxiety, does not have significant associations with weight loss and is still widely used as well.

Therefore, Fen-Phen stands out as the drug specifically associated with weight loss that was ultimately discontinued due to its dangerous side effects.