Acute quinine poisoning produces symptoms such as headache, nausea, rash, ringing in the ears (tinnitus), and possibly heart failure, blindness, or coma. Its toxicity resembles that of salicylates. Chronic quinine poisoning may also cause weight loss, appetite loss, and hypoglycemia.

Dosages of more than 25 milligrams of quinine per kilogram of body weight in adults is usually toxic. Treatment for ingested quinine poisoning generally involves giving the person activated charcoal; other treatment is generally supportive, such as giving intravenous fluids.

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