Hi welcome to health care magic forum. You was taking nortryptiline, from a long time. Now shifted from that drug to the buproprion. You are not comfortable with the buproprion, so want to change back. Since you are using nortryptiline since long time , there is possibility of non availability of the drug for action. Only 50%may be available. I advise you to consult your doctor for change of the drug. He may change to some other drug, and continue for some time more and then if you want can have the nortryptiline. Then it can have full effect. Wishing for a quick and complete recovery.Thank you.