Schematic representation of the proposed mechanism of action of primaquine and carboxyprimaquine against liver hypnozoites. Primaquine (PQ) is metabolized into hydroxylated PQ metabolites (OH-PQm) by CYP2D6. OH-PQm undergoes spontaneous oxidation to quinoneimines (O = PQm) with concomitant generation of hydrogen peroxide (H₂O₂). Primaquine is converted to carboxyprimaquine, the most abundant plasma metabolite, mainly by MAO-A. Carboxyprimaquine produces its own set of quinoneimines that kill the parasite through redox cycling and oxidative damage. Created with BioRender.com. This figure appears in colour in the online version of JAC and in black and white in the print version of JAC.