Robitussin DM cough control?

Hi, I bought some robitussin DM cough control because I could not find
any  cough syrup at my safeway that had just DXM in it. I know this
contains guaifenesin which can cause vomiting in high doses but I just
want to get a light feel for DXM. Has anyone used this cough syrup or
any others with guaifenesin in it? How did you react if so? Thanks!