Cinchonism is a series of symptoms resulting from an overdose of quinine, a compound derived from the cinchona bark used to treat malaria. Symptoms include headaches, nausea, tinnitus, hearing impairment, and mental confusion. Exposure to quinine in tonic water or heart medication can also cause cinchonism. Dosage and patient health affect the severity of symptoms. Physicians must monitor patients closely for adverse events.
Cinchonism, also known as quinism, is a term for a series of disease-like symptoms that result from an overdose of quinine, an alkaloid compound C20H24N2, which is derived from the cinchona bark of the tree and shrub species C. calisaya mainly used to treat drug-resistant cases of malaria. While cinchonism usually occurs from excessive amounts of quinine taken as a medication or through direct ingestion of cinchona bark, it can also be caused by exposure to much smaller amounts of quinine over an extended period. Common symptoms that occur from an antimalarial drug dosage or long-term exposure to quinine include repeated headaches and nausea; tinnitus, which produces a sensation like ringing in the ears; or more severe hearing impairment, including deafness. Rarer cases of adverse effects from cinchonism include anaphylactoid shock; photophobia or sensitivity to light; and mental conditions such as dullness and confusion.
Two other possible methods of exposure can result in symptoms of cinchonism. Tonic water that contains a small amount of quinine to give it a slightly bitter taste can cause cinchonism or the intake of quinidine sulfate, a drug used to treat heart conditions such as ventricular arrhythmia. While tonic water with quinine is generally safe, drinking such water over an extended period of time is theorized to lead to adverse effects. Antiarrhythmic drugs are prone to cause the same level of serious adverse effects as exposure to quinine intake in antimalarial drugs. Drugs like quinidine sulfate, however, have their own additional list of possible side effects, such as blurry vision, potential allergic reactions, and yellowing of the skin.
The dosage of the antimalarial drug can also have a direct effect on the severity of possible symptoms of cinchonism. A standard therapeutic dosage can cause nausea, hearing and vision problems, and various uncomfortable mental states. While these symptoms are reversible and will fade on cessation of the drug, more serious side effects such as blindness, renal failure, and death from cardiotoxicity can occur with higher dosages. Quinine can also have the tragic side effect in high doses of causing birth defects or being an abortifacient, meaning miscarriages can occur in pregnant women who take the drug as a treatment for malaria.
The safety of an antimalarial drug varies greatly based on the patient’s health and dosage. In some cases, only a single dose is needed to cause adverse effects. One reason is that quinine causes certain enzymes to become inactive within mammalian cells, which can have both positive and negative results. It reduces inflammation, which makes antimalarial drugs useful for treating arthritis, but it can also cause a form of muscle disease usually classified as myopathy. These multiple symptoms of cinchonism make it necessary for physicians to evaluate quinine administration on a case-by-case basis and to closely monitor the patient for any adverse events.
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