quinine /kwī″nīn/ [Sp, quina, bark] , a white, bitter, crystalline alkaloid made from cinchona bark. It was formerly used in antimalarial medications and replaced when chloroquine became available. It is once again being used to treat some cases of chloroquine-resistant malaria and is available by prescription for this use. Very dilute amounts of quinine are found in some beverages. See also antimalarial.
