Sudden
withdrawal from venlafaxine can lead to the
withdrawal symptoms you describe. It should not be discontinued suddenly, instead he should go down to 37.5mg for a time before coming off it. Or, his doctor might consider changing him to a different anti-depressant without as many withdrawal symptoms,(Prozac, citalopram ?) then coming off that.
Venlafaxine (Exeffor) is usually prescribed for major depression, in emergencies, or when other anti-depressants have been ineffective.