I've been on mirtazapine for a year, and over time just stopped being effective. Now trying venlafaxine ( effexor ), only been on it for three days but the panic has set in really bad. I know this is all in my mind, after just three small doses should not really notice any difference. Was very anxious about the change, and thought I would be ill, and now fulfilled my prophesy. I'm trying really hard to get a grip, and tell myself that it really is all in the mind but right now feel quite desperate. Has anyone else gone through the same ? Tried to induce a panic attack to get it over with bit couldn't, don't know what else to do, just feel really nervous, panicky and anxious, with scary thoughts.