Can we fire admitted drug user, or should we offer time off for treatment?

Q. We have an employee who has been performing poorly and who has shown up for work appearing to be intoxicated. In a discussion with a manager, the employee admitted that he was currently using cocaine and it was affecting his personal and work life. We haven’t done a drug test on the employee, given his admission of drug use. We want to fire the employee, but we aren’t sure if the FMLA or any other law requires us to give him time off to undergo treatment?