Understanding the Uses and Risks of Quinine and Tonic Water

Quinine is an organic plant-based compound that comes from the Peruvian cinchona tree. It was used by indigenous South American people long before coming to the attention of European explorers. It treated fevers and was effective against malaria, especially when the disease ran rampant. The name "quinine" comes from the Amerindian name for the plant, quinaquina.

The powdered bark of the cinchona tree is bitter, but it was necessary for soldiers traveling to the tropics to take it. To make it palatable, they mixed the medicinal powder with fizzy water and sugar. It was patented as tonic water in the mid-19th century and sold commercially as a prominent alcohol mixer, especially for those who enjoy gin or vodka.

The neuromuscular junction has excitable nerve endings, which can lead to leg cramps, and for years doctors prescribed quinine as a treatment. The drug quells the constant nerve firing at the junction and increases the time between those uncomfortable spasms. While it was somewhat effective, there were numerous side effects, and the FDA banned its use for leg cramps in 2009.

The parasites that cause malaria are transmitted by the infected saliva of the female Anopheles mosquitoes. Because quinine is absorbed quickly in the gastrointestinal tract and metabolized in the liver, it effectively disrupts the parasite's ability to digest hemoglobin. This prevents them from destroying red cells and procreating.

Ringing in the ears — tinnitus — occurs when auditory neurons are continuously activated without the required sound stimulus. Quinine-induced tinnitus isn’t caused by problems with cochlear hair cells, as previously assumed. Research finds that the drug specifically targets and disturbs the ion channels in dopamine neurons. Fortunately, this side effect clears up once people stop using the chemical.

Cinchonism is the overdose of alkaloids from the cinchona plant. One of the side effects is vision loss, which can be temporary or permanent. In one case of acute quinine poisoning, doctors found retinal edema in both eyes that caused noticeable vision loss. There was little or no pupil reaction, and even after 10 weeks, tests showed that all retinal layers were too damaged for more than limited recovery.

Ataxia is a degenerative disease that causes poor coordination and stumbling. Quinine induces cerebellar ataxia, which affects all layers of the cerebellum, impacting the brain's ability to coordinate muscle movements. This condition may go away once treatment ceases, but some individuals require physical therapy to reach their former level of ability.

Quinine-induced thrombocytopenia is one manifestation of quinine sensitivity. It occurs when the drug induces antibodies to destroy platelets, which help the blood clot. A low platelet count means an increased risk of uncontrolled bleeding. Purpura, blood spots that appear on the skin or in the mouth, usually accompany this condition. Corticosteroids can effectively treat thrombocytopenia.

Tonic water has many practical uses. A simple 2 to 1 mixture of water and tonic water prolongs the life of freshly cut flowers. The sugar provides food, and the quinine is a natural preservative. For fresh stains on carpets or clothing, add a bit of tonic water and let the carbonation lift the stain. It’s also good for loosening rusty bolts and cleaning glass.

Those who are on blood thinners cannot take quinine because it increases anticoagulation. Quinine is not recommended for those with arrhythmia, because it will further disturb cardiac rhythms, causing fainting or cardiac arrest. For pregnant women, doctors are cautious about using the drug, except if the mother has malaria. Quinine can pass from mother to fetus, and may cause miscarriage and congenital deformities.