It is even used as the normalizing reference index for a common bitterness index, at least according to Wikipedia.[1]

> In capsule form it's not used much any more for malaria because the taste of the dust on the outside of the capsule made people throw up.

I would suspect that it is not used widely anymore for prophylaxis because there is chloroquine-resistant malaria parasites all over the (malarial) world.[2]

The sell coated capsules, which are't bitter; these have been around for a while [3]

[1] https://en.wikipedia.org/wiki/Bitterant [2] https://www.cdc.gov/malaria/malaria_worldwide/reduction/drug... [3] https://books.google.com/books?id=AjxrAAAAMAAJ&newbks=1&newb...

Yes, that and other reasons. Quinine used to be over-the-counter in the US; people took it for leg cramps. But they made it Rx-only in the 80s (or 90s; not certain) because it can have dangerous side-effects (including cardiac issues) in some people. It's kind of a nasty drug, but it's better than malaria. There are now better drugs for the conditions Quinine was used for.