As previously reported for healthy pregnant women [17], in the GDM group the Cmax values of the (S)-(+)-nor-FLX (7.48 ng/mL) were also higher than those observed for the (R)-(−)-norFLX (3.08 ng/mL) (Table 2 and Figure 2), probably because in both healthy and GDM pregnant women, the (S)-(+)-FLX enantiomer with metabolism dependent on CYP2D6 is metabolized to NorFLX to a higher extent than the (R)-(−)-FLX enantiomer, in which the metabolism is dependent on other CYP isoforms. The gene discussed is CYP2D6; the disease is gestational diabetes.