The present disclosure relates to the use of ferroquine(7-chloro-N-[[2-[(dimethylamino)methyl]cyclopenta-1,4-dien-1-yl]methyl]quinolin-4-amine;cyclopenta-1,3-diene;iron(2+)), or a pharmaceutically acceptable salts thereof for treating and/or preventing infections caused by a parasiteof the species Plasmodium Vivax, the infection of blood cells caused by Plasmodium vivax at the stages of parasitic growth of the immature trophozoite “ring stage” and of the mature trophozoite. In particular use is beneficial in patients deficient in glucose-6-phosphate dehydrogenase.