Ritalinic acid is an inactive, major metabolite of methylphenidate , a schedule II drug in the United States commonly used as a psychostimulant for the treatment of attention-deficit hyperactivity disorder, also known as ADHD. Ritalinic acid is reported to reach plasma concentrations of 1-2 orders of magnitude greater than that of the parent drug and has been monitored in urine to ensure compliance with treatment programs. This product is intended for forensic and biological research purposes.