Chloroquine-d5 diphosphate is primarily used in research and development as a labeled compound for studying the pharmacokinetics and metabolism of chloroquine. It serves as an internal standard in mass spectrometry-based assays, ensuring accurate quantification of chloroquine in biological samples. This labeled compound is particularly valuable in drug development and clinical studies, where understanding the distribution, absorption, and excretion of chloroquine is critical. Additionally, it aids in investigating the mechanisms of action and resistance in malaria treatment, providing insights into optimizing therapeutic strategies. Its application extends to environmental and biochemical studies, where tracking the fate and behavior of chloroquine in various systems is essential.