"a contraindication is a condition or factor that serves as a reason to withhold a certain medical treatment due to the harm that it would cause the patient."

This isn't to say that I have a study or know the efficacy of HCQ. I merely want to point out a flaw in the reasoning of many posters; HCQ being safe for arthritis, lupus, and malaria is not evidence that it is a safe treatment for COVID.

There are some drugs with multitudes more doses than HCQ taken safely and yet they aren't foolproof.

Tylenol is safe. Alcohol is safe. Tylenol + Alcohol is not safe.

Aspirin is safe, but not if you have heart disease (without consideration).

Pseudophed is generally safe but not if you have type 2 diabetes.

Guaifenesin is generally safe but not if you have an overactive thyroid, diabetes, high blood pressure, enlarged prostate, etc.

What's the possibility with COVID?
COVID can attack many parts of the body including the heart, kidney, liver, lungs, white blood cells, etc. HCQ is contraindicated with liver problems, decreased kidney function, low white blood cell count, etc. This overlap is why it shouldn't just be thrown at the wall to see if it sticks.