OXYCONTIN.... You will be able to last for hours
I shouldn't suggest this as it is a DANGEROUS drug, Please be careful when using it. In my city alone there were 27 deaths related to it last year. Oxy is a prescription drug that comes in 10,20,40,80 Miligram Pills and are EXPENSIVE. 50 Cents per mg(40 mg costs $20).
It is really only dangerous if you snort too much. If you snorted 80Mg you will DIE. I suggest you snort 10mg and eat 30mg and only suggest this if you are absolutely sure of what your doing. Oxycontin is a synthetic form of Heroin, which is a CNS depressant, if you do a little too much you will become sluggish and lethargic.
THEY ARE EXTREMELY ADDICTIVE AS ITS AN AWESOME HIGH, IF YOU MAY BE PRONE TO AN ADDICTION, DO NOT TRY THEM.