Oxycodone is a semi-synthetic opiate, 1.5x - 2x as strong as morphine when taken orally. It is one of the most popular recreational opiates.
After swallowing it takes around 1 hour to reach peak levels in your blood stream (only with immediate release versions, not extended release formulations). Though it takes 1 hour to reach peak absorption effects can often be noticed after as little as 10-15 minutes.
Other routes of administration besides taking it orally are problematic. With the exception of injecting, the drug is generally absorbed best orally, though it might work faster when snorted. Oral consumption is the safest and recommended route of consumption.
After reaching peak levels in your blood stream, it will reduce in your blood by 50% over 3-4 hours (again not with extended release versions).
For the opiate naive, a suggested recreational starting dose would be between 10-20mg, with people of lower weight starting closer to 10mg. However some people may require significantly higher doses for effect.
Many side effects may occur, though its usually well tolerated. Generally the most problematic side effects are nausea, dizziness and itching. Rarely a person may have a severe allergic reaction (as people may have to many medications including apsrin). For a more extensive list of possible side effects see General Opiate Side Effects.
Oxycodone as with all opiates is addictive. It usually takes weeks of continual or heavy usage to become physically dependent. Psychological addiction is likely to become reinforced if a cycle develops of running out and experiencing withdrawal symptoms then re-obtaining the drug.
Withdrawal is viewed as extremely unpleasant when severe (though generally not dangerous) with symptoms including:
Anxiety, depression, agitation, nausea, insomnia, gastrointestinal upsets, muscle and other pains, fevers, flu like symptoms , restlessness- especially in the legs.