Bupropion as a modulator of drug activity

A method of treating major depressive disorder, comprising orally co-administering:

• a daily dose of bupropion that is about 150 mg to about 250 mg and a daily dose of dextromethorphan that is about 60 mg to about 100 mg, to a human being in need thereof for at least 8 consecutive days, wherein the bupropion is bupropion hydrochloride, or the free base or another salt form of bupropion and the dextromethorphan is dextromethorphan hydrobromide, or the free base or another salt form of dextromethorphan;
• wherein the bupropion and the dextromethorphan are the only therapeutically active compounds to be co-administered;
• and wherein the dextromethorphan is formulated for immediate release and the bupropion is formulated for sustained release;
• and wherein co-administering the bupropion and the dextromethorphan is more effective in treating major depressive disorder than orally administering the same amount of the bupropion alone for the same number of consecutive days.