The drug in cough syrup that you want is Dextromethorphan (DXM). It can be that intense, depending entirely on dosage. I'll give ya some links,but remember that you wanna find a syrup that ONLY has Dextromethorphan in it. Robotussin Maximum Strength is probably the most potent, but people talk about the gel caps alot too.
http://forum.grasscity.com/pandoras-box/31682-dxm-faq.html <-- The Thread on DXM and extraction
http://www.erowid.org/chemicals/dxm/faq/dxm_faq.shtml <-- a really good FAQ on DXM
http://www.erowid.org/chemicals/dxm/ <-- general info on DXM, including trip reports, and everything else you need to know.
PS: the General forum in the 'Chill Out Zone' is where most DXM-related threads are, so this will probably be moved soon. Try using the search button to find as much as you can. Good luck, and be sure to get all your facts before trying anything.
PS: Coricidin kills