Notes: Ritalinic acid is an inactive, major metabolite of methylphenidate (Item No. 11639), 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.{22009} 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.{25908} This product is intended for forensic and biological research purposes.