Quinine is not enough to just "poison" you, you need a LARGE amount probably straight Quinine to poison you. Quinine is in tonic for the bitter taste, maybe back then it was poisonous since the amount wasnt handled carefully. When was the last time somebody died from drinking tonic water besides if they were allergic to it?
again someone has lost the point entirely. Quinine just from its chemical structure is classed as a poison lol. Doesn't matter if you ingested 1 molecule are trillions of them, your still taking poison into your body.
People die from quinine related problems all the time from the older generation. Using my nana as a good example (although shes still alive). She use to be on quinine sulphate tablets but also drank tonic water, basically killing one of her kidneys off in the process lol.
a lot of people go on holiday having taken quinine based anti malarials and still drink tonic water, usually not feeling too bad on holiday but having to go to hospital soon after they get back home. Whilst working in a pharmacy in a hospital for over a year (before i started uni) I saw quite a few people being treated for quinine poisoning, not earth shattering numbers mind, but more than you'd probably first think.