After a few months of sole phentermine use, patients tend to develop a sort of tolerance to the medication and their weight loss plateaus. Fluoxetine helps to promote the longevity of satiety. When people are full for longer periods of time, this leads to decreased caloric intake.

 

Fluoxetine, commonly known as Prozac, is a SSRI or selective serotonin reuptake inhibitor. It works by increasing the free amount of serotonin in the brain. It is commonly used to treat depression. When pairing fluoxetine with phentermine in this setting, it is solely being used for weight loss.