A doctor can use any approved drug for any purpose he sees fit.
The FDA does not dictate how medicine is practiced.
Calling it horse de wormer etc... is yet another example of the utter propaganda of the political/media axis that acts as a Ministry of Truth under this TechnoTotalitarianism system.
Not the case for covid. A doctor using anything other than the strict guidelines set forth will be 100 percent liable and lose their license. Following the guidelines they are protected
Here’s why they don’t.
https://www.phe.gov/Preparedness/legal/prepact/Pages/4-PREP-Act.aspx
From Dr. Malone: If the hospital or physician refuses to treat you with anything other than Remdesivir (which has an EUA still outstanding despite failing said trials), dexamethasone, oxygen and a ventilator (which, you remember, Trump bought tens of thousands of for this explicit purpose under the DPA) they are immune from all legal action you may take due to their negligence, even if they KNOW there are other treatment options that, on the science, work.
They lose this immunity if they don’t treat “correctly”.