Pamoic acid disodium salt monohydrate is primarily utilized in the pharmaceutical industry as a counterion in the formulation of long-acting injectable drugs. It forms insoluble complexes with certain basic drugs, enabling their slow release into the body, which is particularly beneficial for medications requiring sustained therapeutic effects. This property makes it valuable in the development of depot injections for treatments such as antipsychotics, antibiotics, and hormone therapies. Additionally, it is used in research settings to study drug delivery systems and improve the bioavailability of poorly soluble compounds. Its role in enhancing drug stability and prolonging action makes it a critical component in advanced pharmaceutical formulations.