There are actually several different types of drug screens. Flexeril will not show up on a standard urine drug screen that is looking for drugs of abuse, such as are done for employment. Flexeril may show up on a urine drug screen that is done if someone comes into the ER with an apparent overdose. In this situation, the urine drug screen will look for a different set of drugs, including tricyclic antidepressants, and the Flexeril is structurally similar to tricyclic antidepressants.
That is true. Employment drug screens are looking for drugs of abuse and do not typically look for muscle relaxers.