Not a question about drug testing. Just doing research on how long opana er stays in your system like your urine and stuff compared to the opana ir. From research online i have found it says 3-5 days but the reason i am asking is because i dont understand how thats possible if the half life for er is 10-12 hours. Im not asking for a drug test question. Im asking because it doesnt make sense if you do the math it would be way longer than 3-5 days if the half life is 10-12 hours for ER.