Sodium 4-Phenylbutyrate is primarily used in the medical field for the treatment of urea cycle disorders. It helps in the removal of excess nitrogen from the body by providing an alternative pathway for nitrogen excretion. This is crucial for patients who have deficiencies in enzymes required for the urea cycle, as it prevents the accumulation of toxic levels of ammonia in the blood.

In addition to its role in treating urea cycle disorders, it has been investigated for its potential therapeutic effects in other conditions such as cystic fibrosis, certain types of cancer, and neurodegenerative diseases. Its mechanism in these conditions often involves its role as a histone deacetylase inhibitor, which can modulate gene expression and promote cellular health.

Furthermore, it is also used in research settings to study protein misfolding and aggregation, which are key factors in diseases like Alzheimer's and Huntington's. Its ability to act as a chemical chaperone helps in stabilizing proteins and preventing their aggregation, making it a valuable tool in biomedical research.