Originally it was used as a pain reliever by the Romans and Greek.
Opium commonly traveled along the Silk Road, and was brought into China and Europe, which started the Opium Wars in the 1800s. Opium dens were popular places for the drug to be bought and sold during this time.
Some of the most common side effects are dizziness, drowsiness, feelings of extreme happiness or sadness, stomach pain, nausea, vomiting, constipation, or headaches.
Some of the more serious side effects are irregular heart rate, chest pain, hives or rash, swelling of the face, difficulty breathing, cyanosis, and seizures.
Oxycodone, along with other opiates, produces euphoric feeling, extreme relaxation, pain relief, and reduced anxiety if taken as prescribed, but is also very highly addictive.