Oxy ~ Different brands, different side effects?

I'm a regular user of oxycodone, I've noticed that certain brands tend to make feel nausea while others not at all.

activis and mbox don't, qualitest does. And I've gotten some 15mg ones with K8 on them, not sure what brand so I call them K8's, those make me sick almost instantly.

Should I be taking/not taking something before snorting to avoid this or is it just an additive?

I don't get to pick my brand since I buy em off the street.