Both fenfluramine and phentermine

. Both fenfluramine and phentermine have been successfully used, alone and in combination, for the treatment of obesity. They apparently reduce appetite by affecting the satiety centers in the hypothalamus. Whereas phentermine is a central nervous system (CNS) stimulant related to the amphetamines and is believed to act by releasing norepinephrine from CNS neurons, fenfluramine causes lethargy and sedation and acts by augmenting serotonin neurotransmission. For this reason, the drugs may be used together without causing excessive CNS stimulation or depression.