To my knowledge skmedline is correct. The lab will contact you if
opiates are discovered in your urine drug test. You'll be given an opportunity to provide documented information from your prescribing physician that explains the positive results. At least that is how it works in my state.
Unless you are applying for a position that deems opiate prescriptions to be dangerous, such as driving, you should not have to be concerned over prescription opiates.
Good Luck to you.