the invention relates to method of preventing or treating a disease related to the 5 - ht 2c receptor and the 5 - ht 6 receptor , comprising administering to a human or animal subject in need thereof a 5 - ht 2c receptor agonist and a 5 - ht 6 receptor antagonist in sufficient amounts to provide a therapeutic effect . the invention also relates to a pharmaceutical composition comprising an effective amount of a combination of a 5 - ht 2c receptor agonist and a 5 - ht 6 receptor antagonist , and optionally a pharmaceutically acceptable carrier .