How do compounding pharmacies operate under FDA regulations, and why are pharmaceutical companies trying to restrict their ability to compound certain medications?

Compounding pharmacies are authorized by the FDA to create medications when there's an official shortage or "backlog" of approved drugs. They can use the same molecules as patented drugs but modify delivery systems and dosages to serve patients when branded medications are unavailable. However, major pharmaceutical companies like Eli Lilly are using their political influence to pressure the FDA to remove drugs from the shortage list, even when they cannot meet market demand. This creates a conflict where life-saving emergency medications (like crash cart drugs in hospitals) rely heavily on compounding pharmacies due to low profit margins, yet Big Pharma seeks to eliminate this competition to expand their market control.