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

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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.

Author Notes

Department of Microbiology, University of Texas Southwestern Medical School, Dallas, Texas.

Launey-Altick Medical and Surgical Clinic, Dallas, Texas.