CYP2D6 and Gynecomastia: Their plausible mechanisms involve the inhibition of CYP2D6 and CYP3A4 by berberine (Guo et al., 2012), which increases the concentration and side effects of mirtazapine (edema of lower limbs and myalgia (Lai et al., 2016)), as well as inhibition of CYPD6 (Guo et al., 2012) that increases concentration and side effects of fluoxetine (gynecomastia (Boulenger et al., 2003)) and mianserin (ventricular arrhythmias (Haine et al., 2006)).