(Antidepressant) Venlafaxine (generic name for Effexor) is a phenethylamine bicyclic derivative, chemically unrelated to tricyclic, tetracyclic or other available antidepressant agents. The mechanism of venlafaxine's antidepressant action in humans is believed to be associated with its potentiation of neurotransmitter activity in the CNS. For the symptomatic relief of depressive illness. The effectiveness of venlafaxine in long-term use (i.e., for more than 4 to 6 weeks) has not been systematically evaluated in controlled trials. Therefore, the physician who elects to use venlafaxine for extended periods should periodically reevaluate the long-term usefulness of the drug for the individual patient.