Hydrocortisone sodium phosphate is a water-soluble sodium salt of the phosphate ester of hydrocortisone, a natural glucocorticoid hormone. This modification significantly enhances its aqueous solubility compared to the parent hydrocortisone, making it suitable for parenteral administration, particularly via intravenous or intramuscular injection. Its primary application is as an active pharmaceutical ingredient (API) in emergency medicine and hospital settings for the rapid treatment of acute adrenal insufficiency (Addisonian crisis), severe inflammatory conditions, allergic reactions, and shock. It acts by binding to glucocorticoid receptors, exerting potent anti-inflammatory, immunosuppressive, and metabolic effects. It is also used in diagnostic tests for adrenal function. As a phosphate ester prodrug, it is rapidly hydrolyzed in vivo by phosphatases to release the active hydrocortisone, providing a quick onset of action. Due to its critical therapeutic role, it is often supplied as a sterile lyophilized powder or solution for injection.