How To Clear Roxy S From The Body?

Hi....I took one Roxys 30 mg today and I have to take a urine screen tomorow at my pain clinic they are making sure the thc is out of my system I quit smoking a month ago how can I get the Roxy out of my system? I haven t done one in three weeks until today I m in a lot of pain and my doc wants to prescribe me medicine but couldn t because of the thc what can I do? Or should I just be honest?