Yes.
The British living abroad, over the years, survived many an epidemic, esp. malaria, by drinking large quantities of gin and tonic.
Tonic is watered down quinine.
It was. There isn't enough quinine in modern tonic water to anything but add a sight bitterness. Anyone buying tonic water for medicinal purpose is wasting their time and money. And good gin doesn't need tonic water to provide its medicinal benefits...
all that glitters is not gold
https://www.medicalnewstoday.com/articles/323692#is-quinine-safe
you’d have to drink almost 20 liters of today’s dilute tonic water daily to achieve the daily dose typically prescribed for malaria.
That may come as bad news for anyone hoping to cure the deadly infection with a nightly tippling session, but it should come as a relief to the rest of us, because quinine comes with side effects
.
https://www.livescience.com/36536-tonic-water-quinine-malaria-health.html