Daily delivery of PQ to G6PD deficient (G6PD−) individuals may result in potentially life-threatening acute hemolytic anemia [15], but work in the 1950s found that weekly PQ dosed at 0.75 mg/kg/week for 8 weeks (PQ0.75) caused considerably less hemolysis in G6PD− African Americans (presumed to have mild G6PD deficiency due to G6PD A−) who were experimentally infected with Chesson strain P. vivax. Decreases in the hemoglobin (Hb) level relative to baseline were 7% during weekly PQ therapy and 20% and 50% with 15 mg and 30 mg, respectively, of daily PQ therapy [16]. This evidence concerns the gene GSTM1 and G6PD deficiency.