As a physician, I don't think you will see doctors prescribing hydroxychloroquine just in case. This is not a benign drug. It has potentially serious life threatening reactions like agranulocytosis, aplastic anemia, thrombocytopenia, seizures, angioedema, Stevens-Johnson Syndrome, cardiomyopathy, hepatic failure, cardiomyopathy, QT prolongation, retinal damage and macular degeneration just to name a few. I am sure there are more if I look it up.
In addition it has many common adverse reactions like dizziness, headaches, nausea, vomiting, stomach cramps, blurry vision,and diarrhea. So doctors are not just going to give this drug out as the previous person stated this is not amoxicillin.