Dextromethorphan (DXM) is the active ingredient in cough suppressants like Robitussin, but it is not found in LSD, commonly referred to as "acid." DXM has psychoactive effects at high doses, but its experiences differ significantly from those of LSD and can be unpleasant, often accompanied by nausea. Caution is advised when using DXM, as it is crucial to ensure that no other active ingredients are present in the cough syrup to avoid serious health risks. For more information, the "William White FAQ" is recommended for those interested in DXM's effects and safety.