Oxymorphone has an average half-life span of seven to nine hours. The type of drug test that you are taking will determine the amount of time it will stay in your system. A urine test will show it in your system for three to four days. In a blood test it will show up for twenty four hours. In a saliva test it will show up for one to four days and in a hair follicle test it can show up for 90 days.