Robitussin Maximum Strength Cough and generic equivalents, which contain only dextromethorphan as the active ingredient, are the favored methods of getting high as a kite from DXM, as they are widely available in the U.S. and do not cause unpleasant side effects like vomiting and slow, excruciating death. (DXM will only make you throw up if you have a weak stomach or get motion sickness; guaifenesin will invariably make you puke your guts out.)
As there is no medical reason for putting DXM in icky syrup rather than tablets or gelcaps, it is suspected that this is done to discourage recreational use. | 
