Flexeril is not a physically addictive drug like an opioid or a benzodiazepine, and is not a controlled substance. Flexeril would not normally be tested for in a routine workplace drug screen; however, there have been reports of Flexeril causing a false-positive result for tricyclic antidepressants (TCAs). Flexeril is closely related structurally to the tricyclic antidepressants, e.g., amitriptyline and imipramine.