One of the newest classes of antidepressants, the selective serotonin and norepinephrine reuptake inhibitors (SNRIs) affect both norepinephrine and serotonin. While low levels of both neurotransmitters are associated with depression, norepinephrine is thought to be involved more with alertness and energy, while serotonin influences mood. By increasing levels of both, SNRIs work on different aspects of depression. Depression drugs included in this class of antidepressants are: Cymbalta (duloxetine), Effexor XR (venlafaxine) and Pristiq (desvenlafaxine), Wyeth's followup drug to Effexor. (source healthyplace.com)