Amoxapine-d8 is primarily used in research and analytical laboratories as an internal standard in mass spectrometry. Its deuterated form ensures accurate quantification of amoxapine in biological samples, such as blood or urine, by minimizing interference from non-deuterated compounds. This application is crucial in pharmacokinetic studies, where precise measurement of drug concentrations is required to understand absorption, distribution, metabolism, and excretion. Additionally, it aids in forensic toxicology for detecting and quantifying amoxapine in cases of overdose or poisoning. Its stability and isotopic purity make it a reliable tool for method validation and quality control in analytical chemistry.