Fig. 1: Pathways for drug transmission into human milk.

¹⁹ Open junctions are the gaps that exist between lactocytes during the first days postpartum and allow easier passage of small and large molecules. These junctions close after a few days, whereupon the passage of molecules is restricted to the transcellular passive diffusion pathway or specific facilitated transport mechanisms. See text. Image produced using NIAID Visual and Medical Arts⁷²