Hi,
This link was embedded in article to homemade tonic water. Doing a search on LTH, I found many people who made homemade bitters used cinchona, which is where quinine originates.
Potential dangers of homemade tonic water (related to cinchona):
Tonic water contains quinine as its active, bittering ingredient. Quinine comes from cinchona tree bark. Homemade tonic waters begin with this tree bark either in chunk or powdered form. The powdered form is particularly hard to strain out of the final beverage, and this could lead to an accidental overdose.
The symptons of cinchonism (from wikipedia):
Symptoms of mild cinchonism (which may occur from standard therapeutic doses of quinine) include flushed and sweaty skin, ringing of the ears (tinnitus), blurred vision, impaired hearing, confusion, reversible high-frequency hearing loss, headache, abdominal pain, rashes, drug-induced lichenoid reaction (lichenoid photosensitivity),[1] vertigo, dizziness, dysphoria, nausea, vomiting and diarrhea.
A scientific paper published in 2007 reported a case of a patient self-medicating for leg cramps with quinine and it turns out he gave himself cinchonism. His systems were intermittent fevers, chills, and tremors for approximately 12 days; general malaise that would begin with a bitter taste in his mouth that wouldn't go away. (On PubMed the article is at PMID: 18004031)
If you use cinchona, you really should read this article.
Regards,