Modaline sulfate is primarily used in the field of psychiatry as an antidepressant. It functions as a monoamine oxidase inhibitor (MAOI), which helps in increasing the levels of certain chemicals in the brain that are responsible for mood regulation. This makes it effective in treating depressive disorders, particularly in cases where other antidepressant treatments have not been successful. It is often prescribed for patients who exhibit symptoms of major depressive disorder or atypical depression. Additionally, its use is carefully monitored due to potential side effects and interactions with other medications and foods, requiring adherence to specific dietary restrictions to avoid adverse effects.