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Dangerous Side Effects of Quinine

By Robert Shifko ; Updated August 14, 2017

Quinine is a medication that is used to treat malaria. Quinine is a naturally occurring plant substance that is native to South America. Currently, treatment of malaria is the only approved use of quinine by the U.S. Food and Drug Administration (FDA). This medication was once believed to have value for the treatment of leg cramps. However, quinine treatments were linked to severe, even fatal medical effects, which prompted the FDA in 1995 to ban the substance for all uses other than treatment of malaria.

Cardiac Arrhythmias

Quinine treatment has been known to cause cardiac arrhythmias. Cardiac arrhythmia is a disruption of the heart's normal beating pattern, causing it to beat too fast, too slow or in an irregular interval. Heart rhythm problems impair the heart's ability to properly pump blood to vital organs and potentially impair the ability to sustain life. Cardiac arrhythmias can be treated by a class of drugs known as anti-arrhythmics or even an artificial pacemaker if the condition is severe enough.


Thrombocytopenia can also be attributed to quinine treatment. This disorder is characterized by a decreased number of platelets in the blood. Platelets are the cells that give blood the ability to clot. Thrombocytopenia can lead to abnormal blood clotting or abnormal bleeding. There often are no symptoms associated with this condition. However, thrombocytopenia may lead to blood clot formation, which can cause headaches, dizziness or tingling in the extremities.

Cinchonism (Mild)

Cinchonism, also known as quinism, is a medical condition in humans that occurs from an overdose of quinine. There are several medical symptoms associated with cinchonism. Individuals who acquire this condition may experience flushed or sweaty skin, ringing in the ears, confusion, blurred vision, abdominal pain and headache. These effects generally occur with a small overdose when a therapeutic dose of quinine is given, or with long-term use of products that contain quinine, such as tonic water. Large overdoses of quinine have effects that are far more severe.

Cinchonism (Severe)

There is an extremely small margin for error when dealing with quinine doses and treatment. There is a very small difference between correct dose and overdose. Severe overdoses of quinine can have potentially fatal consequences. Major overdoses of quinine can cause cardiotoxic effects such as hypotension, cardiogenic shock and life-threatening cardiac arrhythmias. A major overdose of quinine may also have toxic effects to the central nervous system, causing loss of consciousness, seizures and coma. In addition, toxic levels of quinine may cause respiratory abnormalities such as pulmonary edema (lungs fill with fluid) and adult respiratory distress syndrome (severe lung disease which may lead to multiple organ failure and possibly death).

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