My Husband Takes An Antidepressant By The Name Of Fluoxetine.

my husband takes an antidepressant by the name of fluoxetine. He has been taking it for 20 years off and on. His depression started at that time because his brother had committed suicide. Today our Dr. prescribed another drug Pristiq (desvenlafaxine) because he is not feeling better on the fluoxetine. I don't feel that he should be going off the fluoxetine cold turkey before this other drug. Please contact me with info. I want what's best for him. His brother was also on an antidepressant at the time of his death. Please give me the knowledge so I can give him the best decision.