Observations on Two Plasmodium Falciparum Infections with an Abnormal Response to Chloroquine

Abstract

Summary The first of two patients with Plasmodium falciparum infections which failed to respond to chloroquine therapy administered in Colombia, South America, received three further courses of 1.5 g of chloroquine and experienced clinical and parasitic relapses 12 and 8 days, respectively, after the first two courses. Upon the completion of the third course the drug was continued for 14 more days at a dosage of 0.3 g daily. Blood smears remained positive during this period. A 3-day course of quinine sulphate (90 grains) produced negative blood smears, but a parasitic relapse occurred after 17 days. An apparent cure was effected by a 10-day course of quinine. The second patient experienced a clinical and parasitic relapse approximately 20 days after a first course of chloroquine; and after a second course (2.1 g) followed by a 14-day course of primaquine, a recurrence of parasitemia accompanied by minor symptoms approximately 21 days after the completion of the chloroquine therapy was observed. A 10-day course of quinine produced an apparent cure.