What are your rights if fired for a false positive drug test due to over the counter medication?

Under the laws of all states in this country one's employement is terminable at the will of an employer so long as the termination is not based upon Constitutional protected areas of discrimination.

Your recourse is to get a medical letter from your treating physician setting forth the reasons for the reault for the false positive and hope that you get your position back when submitted to your former employer.