Is there something in quinine that may affect a pilot enough that there is a regulation against

drinking it before flights?

I think it can cause heart fibrillation, but it’s really rare.

I could be wrong but I thought ex-pat pilots in PNG took quinine to combat malaria.

List of possible side-effects of quinine.

Note in particular the neurological side-effects.

The amount of quinine in modern tonic is tiny compared to that which might be found in a therapeutic dose however.

I once heard that a ‘passed quietly from mother to daughter’ method to induce miscarriage involved quinine consumed in a particular manner.
Never even tried to confirm it (I’m male - Mommy taught me basic sewing, cooking, and even laundry, but we never mentioned unwanted pregnancy).

FAA, pilots, and drinking:
It has changed recently (as has the general perception of "drinking and driving’), but 10 years ago or so, the the FAA rule was ‘8 hours from bottle to throttle’ - it is not like them to be overly concerned about quinine.

Years ago there was some concern that chronic long term consumption of beverages containing quinine would eventually do damage to the balance mechanism of the inner ear. Which would obviously be adverse to a pilot’s long term career prospects.

But AFAIK there was never a prohibition by USAF or FAA against individual consumption of such beverages. There certainly is no such prohibition now.
Switching gears away from beverages …

There are many medications that FAA says can’t be taken while flying. In most cases the issue isn’t the medication itself, but rather the fact that if you’re taking medicine X then you have disease Y and they don’t want folks with an active case of Y flying.

And yet they think it’s OK for people who have disease Y to fly as long as it’s untreated. I guess I don’t understand how these things work.

I thought it was 8 meters, have I been doing it wrong all these years? hic

You’re right; you don’t understand how these things work.

Pilots are required to report any and all health concerns to the FAA and also report all encounters with the medical industry, including routine checkups. It is a violation of regulations to fly while knowing, or reasonably suspecting, that you have a chronic untreated condition.

What we don’t have today is intrusive Big Brother enforcement of this wherein all e-med records everywhere are sent to FAA and all pilots receive a comprehensive stem-to-stern all-possible-diseases workup by some hostile government doctor every 6 months. Plus a session or two with a hostile government shrink.

Yet.

Not directly related to the OP, but I mention it because of a local story (to me) of a woman who committed suicide after taking mefloquine, which her family blames as the cause.

[My bold]

Not exactly quinine, and as mentioned above, medicinal doses would be much higher than in a serving of tonic.

The shrink thing was brought to the fore, at least publicly for a wide audience, with the GermanAir suicide/mass murder.

Medicinal tonic water originally contained only carbonated water and a large amount of quinine. However, most tonic water today contains a less significant amount of quinine, and is thus used mostly for its flavor. As a consequence, it is less bitter, and is also usually sweetened, often with high fructose corn syrup or sugar. Some manufacturers also produce diet (or slimline) tonic water, which may contain artificial sweeteners such as aspartame. Traditional-style tonic water with little more than quinine and carbonated water is less common, but may be preferred by those who desire the bitter flavour.

In the United States, the US Food and Drug Administration (FDA) limits the quinine content in tonic water to 83 ppm[3] (83 mg per liter if calculated by mass), while the daily therapeutic dose of quinine is in the range of 500–1000 mg,[4] and 10 mg/kg every eight hours for effective malaria prevention (2100 mg daily for a 70 kg adult).[5] Still, it is often recommended as a relief for leg cramps, but medical research suggests some care is needed in monitoring doses.[6] Because of quinine’s risks, the FDA cautions consumers against using “off-label” quinine drugs to treat leg cramps.[7]

This is probably what I what trying to think of when I wrote my post above about neurological side-effects of quinine. Mefloquine has been controversial because of the reports of serious and long-term neuro-psychiatric adverse effects:

There are 150 people who died in the Alps a few months ago because a pilot did not do this.

More mefloquine horror stories.

Crazy Pills, David Stuart MacLean, New York Times, Aug. 7, 2013.

Another nightmare account of Lariam adverse effects, Homecoming Vets web site (a re-post of an earlier article from somewhere else).

All pilots, or just (or mainly) commercial pilots? What about private non-commercial pilots?

I’ve never had occasion to take mefloquine (Lariam) but I’ve dispensed it many times, and have also heard many times that people often prefer having malaria to taking that dreadful stuff. Fansidar, a combination product, is less unpleasant, but more expensive and has to be taken every day, vs. weekly for Lariam.

Now back to our regularly scheduled programming.

The regs don’t distinguish. As a practical matter (ref other posts) we see a lot more public concern with these issues with commercial pilots as opposed to hobbyist pilots.