Quinine Hydrochloride is an alkaloid of cinchona that was once widely used to control and prevent malaria; it also has analgesic, antipyretic, mild oxytocic, cardiac depressant, and sclerosing properties, and it decreases the excitability of the motor end plate. It is used as the dihydrochloride, hydrochloride, or sulfate salt in the treatment of resistant falciparum malaria.
Quinine Hydrochloride occurs naturally in the bark of the cinchona tree, though it has also been synthesized in the laboratory. The medicinal properties of the cinchona tree were originally discovered by the Quechua, who are indigenous to Peru and Bolivia; later, the Jesuits were the first to bring cinchona to Europe.
Quinine Hydrochloride can cause abnormal heart rhythms, and should be avoided if possible in patients with atrial fibrillation, conduction defects or heart block. Quinine can cause hemolysis in G6PD deficiency (an inherited deficiency), but this risk is small and the physician should not hesitate to use quinine in patients with G6PD deficiency when there is no alternative.