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Cinchonism or quinism is a pathological condition in humans caused by an overdose of quinine or its natural source, cinchona bark. Quinine is used to treat resistant malaria, nocturnal muscle cramps and can also act as an abortifacient. In much smaller amounts, quinine is an ingredient of tonic drinks, acting as a bittering agent. Cinchonism can occur from therapeutic doses of quinine, either from one or several large doses, or from small doses over a longer period of time, but not from the amounts used in tonic drinks. Symptoms of mild cinchonism (which may occur from standard therapeutic doses of quinine) include flushed and sweaty skin, tinnitus, blurred vision, impaired hearing, confusion, reversible high-frequency hearing loss, headache, abdominal pain, rashes, lichenoid photosensitivity [1], vertigo, dizziness, dysphoria (feeling uneasy), nausea and vomiting, and diarrhea.
Large doses of quinine may lead to severe symptoms of cinchonism: skin rashes, deafness, somnolence, diminished visual acuity or blindness, anaphylactic shock, and disturbances in cardiac rhythm or conduction, death from cardiotoxicity.
Patients treated with quinine may also suffer from hypoglycemia (especially if administered intravenously) and hypotension (low blood pressureBlood pressure or arterial blood pressure is the pressure (force per unit area) exerted by the blood on the walls of the blood vessels. Unless indicated otherwise, blood pressure refers to the pressure in the large arteries, such as the brachial artery (i). In very high doses (higher than those used to treat malaria) during the first trimester of pregnancy quinine may act as an abortifacient, or cause birth defectA birth defect is a physical or mental abnormality present at the time a child is born. Birth defects range from minimal, such as birthmarks, and slightly mobility-impairing, such as amelia of the legs, to very serious, such as cerebral palsy, and incompas, especially deafness.
Most symptoms of cinchonism (except in severe cases) are reversible and disappear once quinine is withdrawn.
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