I took a oxycodone and i'm feeling kinda drowsy . how long will that last ?

About 4-5 hours: Half life of oxycodone is about 4-6 hours which means half of the drug is metabolized by the body. It is possible that it is a little longer. Avoid use of any machinery including driving.

Within 5 hours: In general oxycodone by mouth (PO) 5 mg will have its "peak effect" from 0.5-1 hour, will have a "duration of action" of between 3-6 hours, and half of it will be eliminated (half-life) from the body within 2-5 hours. So, your drowsiness, a typical effect of this drug, would be expected to decrease within this mid range...Physical conditions and interference from other drugs can change this!