Bupropion as a modulator of drug activity

A method of treating major depressive disorder, comprising orally administering a dosage form once or twice a day for at least 8 consecutive days to a human being suffering with a symptom of major depressive disorder;

• wherein the dosage form comprises, as the only therapeutically active compounds in the dosage form:
• 1) about 100 mg to about 110 mg of bupropion hydrochloride, or a molar equivalent amount of a bupropion in the free base form or another salt form, and 2) about 40 mg to about 50 mg of dextromethorphan hydrobromide, or a molar equivalent amount of a dextromethorphan in the free base form or another salt form;
• and wherein the dosage form provides sustained release of bupropion.