Chloroquine: physiological basis of drug resistance in Plasmodium berghei.

Mouse erythrocytes, parasitized by chloroquine-sensitive plasmodia, concentrate this drug in vivo to levels over twice as high as erythrocytes parasitized by chloroquine-resistant plasmodia; nonparasitized red cells accumulate little chloroquine. Selective toxicity of this drug may depend upon a special drug-concentrating mechanism of plasmodic impairment of such mechanism.