I have had panic disorder and depression for years. I maxed out Prozac and was put on welbutrin xl 150. I went up to 300 pretty shortly after and it was fine. Suddenly my panic attacks came back and they r debilitating. The doctor put me on the highest dose of welbutrin xl 450mh. 300 in the am and 150 in the pm. I started yesterday but waking up w panic and suffering daily sucks. How long will it take before I know it isn't working and I have to switch?