The control group was much younger on average, so perhaps that explains why they didn't lose any patients.

In addition, what about long term effects? Curing someone now, and giving them a stroke six months later is not exactly desirable. That's why drug trials last for such a long time.

Hydroxychloroquine is not a new drug. It is known to be associated with some serious side effects, but stroke isn't one of them.

There's always possibility of interaction of a the drugs effects with disease state to cause new side effects. It may not be likely, but there's always a chance, which is why it would be monitored for as usage of a drug grows.

There's a likelihood of interaction in this case as they both have side effects on the heart. It should probably be monitored carefully in hospital this case.

As I understand it, this drug is used daily by people with conditions such as lupus so there’s some knowledge about long term effects at a given dosage.

Yes, but only when treating lupus!

The dosage rates are about the same as other use-cases and within safe boundaries.

Toxicity is typically tied to dosage rates or drug interactions. The bigger concern from the french study was the additional use of Azithromycin which is more dangerous/toxic. The dosage rates and toxicity of HCQ by itself is well known.

The other big risk is panicky people ignoring the recommended guidelines. Fortunately in the US (and Canada) both drugs require a prescription where both a doctor and pharmacist will provide this information, and it will be printed on the pillcase. What's more worrying is people buying it in countries where it's over the counter then not reading the side of the box and taking far too much (or worse reading the correct dose and thinking 2x the drug = 2x more effective or some nonsense).

It's (used to be?) a prophylactic for malaria. Literally billions of people took it. I did it myself when I was living in malarial areas. It does have secondary effect but they're very well-known and for most people the only ill effect is that it tastes incredibly foul.

It is a great question. As I understand it, we know a lot more about the long term effects of Hydroxychloroquine than we do about the long term effects of covid19.