Phen-Pro is the name given to the combination of phentermine and a low dose of one of the following: Prozac, Zoloft, Celexa, Luvox, trazodone, or Effexor. Although these second medications in the Phen-Pro combination are anti-depressants, their prescription alongside phentermine is not for the treatment of depression but rather is intended to help the phentermine work more effectively at promoting weight loss. Dr. Michael Anchors, who developed Phen-Pro and holds the patent for this combination, first tested the combination of phentermine and Prozac in 1995 and, based on his findings, believes that the addition of Prozac makes phentermine work more effectively and for a longer period of time.
Prozac, and other anti-depressants in the Phen-Pro combination, are types of Selective Serotonin Re-uptake Inhibitors (SSRIs), and are believed to increase the level of the neurotransmitter serotonin by inhibiting its reuptake. Serotonin is a naturally occurring appetite suppressant which curbs cravings and cuts off appetite, meaning that you will feel satisfied even when your stomach is not full. Therefore, it is thought that the combination of phentermine and the additional levels of serotonin promoted by the SSRI ingredient of Phen-Pro work together to inhibit appetite and help you lose weight by controlling hunger.