G6PD and G6PD deficiency: Both primaquine and tafenoquine cause drug-induced hemolysis in persons with glucose-6-phosphate dehydrogenase (G6PD) deficiency.6-8 This X-linked enzymopathy has a prevalence of 1 to 30% in populations at risk for P. vivax malaria.9 Currently available qualitative G6PD rapid tests use a threshold of G6PD enzyme activity of approximately 30% of normal (defined as the median value among healthy male volunteers) to classify persons as G6PD deficient.