Also go to drug store and
buy a five panel urine drug screen. It will tell you
in moments if they are using oxy, coke, heroin, weed, or meth.
Maybe they are smoking some other drug than oxy. The bottom line is they should not be swallowing oxy much less snorting or smoking it.
Make them take a pee test. If they refuse they are guilty. This is very important what I'm going to say, you must at all cost observe the urine leave their body into sample cup.