Well, first off, I'm not sure why you would be prescribed oxycodone AND Tylenol 3 at the same time??? I've been on oxycodone for a very long time so I feel I can speak about side effects: drowsiness, euphoric feeling, hot flashes, constipation, itching, nausea, vomiting and extra energy. Most of those go away after a little bit of time. (And these are the ones I experienced. There may be more.) The constipation can be really bad. I take stool softeners or Miralax.