You should be able to perform the extraction on the generic tussin but don't use Delsym. Delsym contains Dextromethorphan polistirex not DXM hydrobromide (HBr). I am not familiar with the chemistry of the polistirex form but I am sure that you won't be able to perform an extraction which is essentially an A/B extraction or B/A in this case. You would need the HBr form as the polistirex form is not an acid salt, it is some weird type of polymer that coats the molecule allowing it to be slowly absorbed by the body aka time release. So as long as Dextromethorphan hydrobromide is your only active ingredient you are good to perform your extraction. The brand does not matter only what ingredients are within. Once you add your ammonia or whatever base you are using, the DXM will separate from the cough syrup inactive ingredients. That is when you add a non polar solvent, react, discard polar layer and proceed to either evaporate the DXM/solvent layer to obtain freebase DXM or add an acid and evaporate solvent to leave you with a DXM salt. Most people use lemon juice to procure DXM citrate.