Deferasirox-d4 is primarily used as an internal standard in bioanalytical studies, particularly in pharmacokinetic and metabolism research. It supports accurate quantification of deferasirox in biological samples using mass spectrometry techniques like LC-MS/MS. Due to its stable isotope labeling, it closely mirrors the behavior of the unlabeled compound during sample processing, ensuring high precision and reliability in drug concentration measurements. This makes it essential in clinical trials and therapeutic drug monitoring where exact measurement of deferasirox levels is critical for assessing efficacy and safety.