Irinotecan-d10 is primarily used in research and development as an internal standard in analytical chemistry. It aids in the accurate quantification of irinotecan and its metabolites in biological samples through techniques like liquid chromatography-mass spectrometry (LC-MS). This application is crucial in pharmacokinetic studies, helping to understand drug absorption, distribution, metabolism, and excretion. It also supports therapeutic drug monitoring, ensuring optimal dosing and minimizing toxicity in cancer treatment. Additionally, it plays a role in the development and validation of bioanalytical methods, ensuring precision and reliability in drug analysis.