In order to passively diffuse through the blood-brain barrier,a drug must:
A) lipid soluble, charged, and relatively small.
B) water soluble, charged, and relatively small.
C) lipid soluble, uncharged, and relatively small.
D) water soluble, uncharged, and relatively large.

Question

Quizplus · Accepted Answer

The blood-brain barrier is composed of tight junctions between endothelial cells that line blood vessels in the brain. In order to pass through this barrier, a drug must be able to cross through these cells. Lipid-soluble drugs can diffuse through the lipid bilayer of the cell membranes, while uncharged and small drugs can move through the water-filled pores between cells. Charged and large drugs, in contrast, cannot pass through the barrier. Therefore, the best choice is C, which describes a lipid-soluble, uncharged, and relatively small drug.

In Order to Passively Diffuse Through the Blood-Brain Barrier,a Drug