Q. I have been drinking a liter or two of tonic water a week for nearly 25 years. Now I’m reading about risks associated with quinine. How much is too much? How much quinine is in tonic? What are the side effects? Should I stop drinking tonic water?
A. Quinine has been used medicinally to ward off malaria since the 17th century. The normal dose to treat malaria is 648 mg every eight hours for a week. A glass of tonic has roughly 20 mg, so you can see that there is a big difference in dose.
Some people are so susceptible to serious side effects from quinine that they must avoid even the small amount in tonic water. For them, quinine may cause life-threatening heart rhythm disturbances, severe skin reactions and several blood-related complications. That is why the FDA banned quinine for treating leg cramps.
Since you have not experienced any complications for 25 years, it is unlikely that you need to give up tonic. A glass or two daily should not cause you problems.