Desvenlafaxine (brand names: Pristiq, DESFAX), also known as O-desmethylvenlafaxine, is an antidepressant of the serotonin-norepinephrine reuptake inhibitor (SNRI) class developed and marketed by Wyeth (now part of Pfizer). Desvenlafaxine is a synthetic form of the major active metabolite of venlafaxine (sold under the brand names Effexor and Efexor). It is being targeted as the first non-hormonal based treatment for menopause. More: en.wikipedia.org.