Used primarily as a metabolic byproduct of methylphenidate, ritalinic acid serves as a key biomarker in drug testing and pharmacokinetic studies. It helps in monitoring the presence and duration of methylphenidate in the body, especially in urine screening for stimulant use. Due to its longer half-life compared to the parent compound, it improves the detection window for methylphenidate in forensic and clinical toxicology. Ritalinic acid is also used in research settings to evaluate metabolic pathways and enzyme activity involved in the breakdown of central nervous system stimulants.