It is unknown how exactly oxycodone works. Opioid receptors are increased and delivered to nerve terminals in the heart, lungs, liver, gastrointestinal tract, and reproductive system when there is inflammation or hyperalgesia. Opioid agonists include oxycodone and its active metabolites noroxycodone, oxymorphone, and noroxymorphone. The blood brain barrier is either passively crossed by these substances or it may be actively crossed by an unidentified mechanism.