Cinchonism

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, not from the amounts used in tonic drinks, but possibly from ingestion of tonic water as a beverage over a lengthy period of time. Quinidine (Class 1A anti-arrhythmic) can also cause cinchonism.

Signs and Symptoms
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, lichenoid photosensitivity, 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. Quinine overdose can also result in a rare form of hypersensitivity reaction termed blackwater fever that results in massive hemolysis, hemoglobinemia, hemoglobinuria, and renal failure.

Patients treated with quinine may also suffer from hypoglycemia (especially if administered intravenously) and hypotension (low blood pressure). 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 defects, especially deafness.

Most symptoms of cinchonism (except in severe cases) are reversible and disappear once quinine is withdrawn.