Fig. 1
From: The opioid epidemic: a central role for the blood brain barrier in opioid analgesia and abuse
Model of the of the neurovascular unit with a diagram indicating the relative brain penetrance of selected opioids. Endothelial cells surround the capillary lumen. P-Glycoprotein (green ovals) in the luminal membrane effluxes many types of opioids (red/blue circles) back into the circulation. Additional transporters (purple/orange) at the luminal membrane transport specific opioid analogs. In the methadone figure, the red and blue circles represent different methadone enantiomers