Drug testing question?

My doctor has me on the drug Opana ER for RSD in my hand. It is a relief to finally have something that helps my pain. Here is my question, I went on a job interview and got the job...(hurray) there is a company car involved. I do not take the Opana during the day even though it is prescribed for me too because i have a 6 year old and i am scared if i have to drive i could have an accident. Anyway, I have to have a drug test for the job, is Opana going to show up? Should I tell the tester that i am taking it? I could try not taking it for 3-4 days but my pain would be out of control......thanks for your help