HomePhentermine FAQsWhat is Phen-Pro?What is Phen-Pro?Phen-Pro refers to the combination of phentermine and a low-dose antidepressant such as Prozac (“pro”), Zoloft, Celexa, Luxor, Effexor or trazadone. Some doctors believe this combination prolongs phentermine’s effectiveness.All of these anti-depressants are in a class of medications called selective serotonin reuptake inhibitors (SSRIs). In addition to keeping you happy, serotonin also sends signals of fullness to your stomach. So, these medications help you feel fuller faster. When combined with phentermine’s appetite suppressant and energy boosting properties, the combination makes a powerful weight loss prescription.NEVER mix these medications without a doctor’s explicit direction to do so. Combining these medications in high doses or in certain conditions can prove dangerous, or even fatal.→ Click here to read more about phentermine combinations.