Will oxycodone effect you more if you take the drug rectally?

No. The absorption of any opiate depends on the form (liquid/solid/gas) and the route of administration (oral, intravenous, rectal, inhaled). While there are some advantages of certain routes of administration which bypass initial degradation by the liver, for the most part rectal administration (ie "up the butt") is not likely to lead to higher or quicker blood levels. IF you wanted to have greater rectal absorption, I would suggest a liquid, an opiate with greater absorption characteristics (fentanyl, for example) and prolonged contact time (holding an enema for example). This still has the dangers of overdose (death or respiratory depression with aspiration) since it is hard to judge the effect in advance. I would suggest sticking to swallowing your oxycodone.