hello ma m, Thanks for approaching healthcare magic and first of all let me appreciate you for recognizing that your kid has been on oxycontin illegally. yes it is a narcotic analgesic having potential for addiction.Respiratory depression (breathing problems) could occur with the use of oxycontin and this could be fatal. other side effects could be constipation, nausea, sleepiness, vomiting, tiredness, headache, dizziness and abdominal pain. I would suggest to take her to a rehab center as it could save her from lifethreatening fatalities with the addictive drug. Please get back for further queries. Thank you once again.