Blood-brain Barrier Passage Does Pb Cross the Blood-brain Barrier during Conditions of Stress?

Pyridostigmine bromide is a carbamate AChE inhibitor with a positively charged “quaternary ammonium” group, which is believed to prevent its penetration through the “blood-brain barrier,” a layer of cells that controls which substances may penetrate from the general circulation into the brain. Therefore, side effects of PB are typically those of heightened peripheral cholinergic activity (nicotinic and muscarinic). PB has been perceived as having an enhanced safety profile relative to such other carbamates as physostigmine, because of its relative disinclination to penetrate the blood-brain barrier. However, recent evidence suggests that PB can cross the blood-brain barrier under some circumstances, specifically in the context of stress or chemical combinations.