Used primarily in research and development, it serves as a stable isotopically labeled internal standard in analytical methods. This aids in the precise quantification and detection of azelastine in various biological matrices, such as plasma or urine, during pharmacokinetic studies. Its application ensures accuracy and reliability in studies focused on understanding the drug's metabolism, distribution, and excretion in the body. Additionally, it supports the development of sensitive and specific assays for therapeutic drug monitoring and clinical research.