Okay Reddit, I need your expertise, please help...

This is a throw away just in case, I got offered a job I've been searching for for a long time now. It's something I really really want and enjoy doing. Now note I promise that I don't do drugs, but the problem is that they require a list of over the counter and prescription drugs I have taken within the last thirty days. All of this is okay except a week ago I took a muscle relaxer that my mother had given me for my scoliosis. The problem is that it was her prescription and not mine.

I only took one because my muscles were hurting really bad to the point I could not breath. I took the pill which was 10 mg. last Saturday the 16th. and I take the drug test the 29th.

I have taken a few A&P classes and know what a half life of medicine is and I tried calculating it but I'm honestly not completely sure if it will be out of my system. I just want to ask Reddit for guidance and opinions on what I should do.

The drug was Flexeril (Cyclobenzaprine) 10 mg. and the half life is 18 hours.

TDLR, I took a drug that was my moms' for scoliosis and I have a drug test to take and not sure if I should say anything or not.

Please help Reddit.