Described herein are dosage forms of enantiomerically enriched (S)-bupropion or enantiomerically enriched (R)-bupropion. The (S)-bupropion or the (R)-bupropion may be deuterium enriched, or may have natural isotopic abundance. These dosage forms may be administered, either fed or fasted, to treat a condition recited herein, to achieve a certain pharmacokinetic parameter of a bupropion or a metabolite of a bupropion, and/or to enhance dextromethorphan plasma levels.
