The influence of chloroquine and quinine on the CYP2D6-mediated formation and kinetics of 3-hydroxyprimaquine from racemic PQ (a) and its individual enantiomers (b, c); and on the formation of 4-hydroxyprimaquine from racemic PQ (d) and its enantiomers (e, f). Each point represents values mean ± S.D. (n = 4)