Somebody help me out here....

One of the legitimate uses for hydroxychloroquine is the treatment of lupus. But lupus patients are having a hard time getting their prescriptions filled because of a shortage caused by people using the drug as an unproven and very dubious treatment for COVID-19.

What I would like to know is this:

Hydroxychloroquine is a regulated prescription drug. The only way to get it is if a doctor signs a prescription. So how are enough people getting hold of it to create a shortage? Are doctors not ethically barred from prescribing potentially harmful drugs when there is no evidence that they will benefit a patient? Has advertising prescription drugs to the general public so broken the system that a patient feels he has a right to simply tell a doctor what drug to prescribe? And does the doctor then just write the scrip, consequences be damned?