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Quinine

The original antimalarial agent, quinine took its name from the Peruvian Indian word "kina" meaning "bark of the tree" referring to the cinchona tree. From this tree, quinine was first obtained. The Peruvian Indians called it "the fever tree." Quinine, a large and complex molecule, is the most important alkaloid found in cinchona bark. Until World War I, it was the only effective treatment for malaria. In fact, quinine was the first chemical compound to be successfully used to treat an infectious disease. Quinine was isolated in crystalline form in 1820 by J.B. Caventou and P.J. Pelletier. In one of the classical achievements of synthetic organic chemistry, R.B. Woodward and W. Doering first made synthetic quinine in 1944. Quinine acts by interfering with the growth and reproduction of the Plasmodium, the malarial parasite that lives within the victim's red blood cells. Quinine causes the parasites to disappear from the blood and the symptoms of the disease are thereby alleviated. However, when quinine treatment ends, many patients relapse. They suffer another attack of malaria due to the failure of quinine to kill the malarial parasites in cells of the body other than the red blood cells. These parasites persist and, after a time, they reinvade the red blood cells and precipitate the relapse. Since quinine does not permanently cure malaria, better drugs were sought. A number were discovered that replaced quinine during and after World War II. Some of these drugs (such as chloroquine and chloroguanide) are more effective than quinine in suppressing the growth of the blood forms of the malarial parasite. Others (such as primaquine and pyrimethamine) act upon both the blood and tissue phases of the parasite, producing a complete cure and preventing a relapse. Quinine has been used outside of malaria as a remedy for fever and pain and to treat and prevent leg cramps. Prolonged administration of quinine may produce toxic symptoms such as deafness, disturbances in vision, skin rashes, and digestive upsets.

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The most important of the alkaloids derived from cinchona; an antimalarial effective against the asexual and erythrocytic forms of the parasite, but having no effect on the exoerythrocytic (tissue) forms. It does not produce a radical cure of malaria produced by Plasmodium vivax, P. malariae, or P. ovale, but is used in the treatment of cerebral malaria and other severe attacks of malignant tertian malaria, and in malaria produced by chloroquine-resistant strains of P. falciparum; it is also used as an antipyretic, analgesic, sclerosing agent, stomachic, and oxytocic (occasionally), and in the treatment of atrial fibrillation, myotonia congenita, and other myopathies.

- q. bisulfate the acid sulfate of q., very soluble in water.

- q. carbacrylic resin resin.

- q. ethylcarbonate an almost tasteless form of q. that is poorly absorbed from the intestinal tract.

- q. sulfate the most frequently prescribed salt of q..

- q. and urea hydrochloride sclerosing agent for treatment of internal hemorrhoids, hydrocele, and varicose veins, containing not less than 58% and not more than 65% of anhydrous q..

- q. urethan a mixture of urethan and q. hydrochloride; a sclerosing agent for the treatment of varicose veins.

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qui·nine 'kwī-.nīnalso 'kwin-.īn, esp Brit kwin-'ēn, 'kwin-ēn n a bitter crystalline alkaloid C₂₀H₂₄N₂O₂ obtained from cinchona bark that is used as a flavoring agent, has antipyretic and analgesic properties, and is administered orally in the form of its salts (as the hydrated sulfate (C₂₀H₂₄N₂O₂)₂·H₂SO₄·2H₂O) as an antimalarial

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a drug used to prevent and treat malaria, now largely replaced by more effective less toxic drugs except in cases of malaria due to Plasmodium falciparum. It is administered by mouth or injection; large doses can cause severe poisoning, symptoms of which include headache, fever, vomiting, confusion and damage to the eyes and ears (see cinchonism). Small doses of quinine are used to treat muscular cramps.

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qui·nine (kwinґin) (kwin-ēnґ) (kwiґnīn) [L. quinina] an alkaloid of cinchona, which suppresses the asexual forms of all malarial parasites during the erythrocytic stage and has a slight effect on Plasmodium vivax and P. malariae during the gametocyte stage. Once widely used to prevent and control malaria, it has been largely replaced by less toxic and more effective synthetic antimalarials, and is now used chiefly (usually in the form of one of its soluble salts) in the treatment of falciparum malaria resistant to other antimalarials. Quinine also has analgesic, antipyretic, mild oxytocic, cardiac depressant, and sclerosing properties, and it decreases the excitability of the motor end plate.

Medical dictionary. 2011.