Risperidone-d4 is primarily used in research and analytical laboratories as an internal standard in mass spectrometry and chromatography studies. It helps in the accurate quantification and identification of risperidone and its metabolites in biological samples, such as blood, plasma, or urine. This deuterated compound is particularly valuable in pharmacokinetic studies, drug metabolism research, and forensic toxicology, where precise measurement of risperidone levels is essential. Its use ensures improved accuracy and reliability in analytical methods due to its stable isotopic labeling, which minimizes interference during analysis.