Which statement best describes the distribution of highly lipid-soluble drugs?

Which statement best describes the distribution of highly lipid-soluble drugs?

• A. They are taken extremely quickly to the brain
• B. They remain confined to plasma
• C. They distribute only to the liver
• D. They do not cross cell membranes

Answer: (A)

Highly lipid-soluble drugs cross cell membranes readily by passive diffusion, so they rapidly distribute into tissues with high perfusion, especially the brain. Their lipophilicity allows easy passage across the blood-brain barrier, causing swift CNS delivery. Because they leave plasma and distribute into tissues (and even adipose tissue), they are not confined to plasma, nor restricted to the liver, and they do cross membranes. Thus, the best description is that these drugs reach the brain very quickly due to easy membrane permeation.

Highly lipid-soluble drugs cross cell membranes readily by passive diffusion, so they rapidly distribute into tissues with high perfusion, especially the brain. Their lipophilicity allows easy passage across the blood-brain barrier, causing swift CNS delivery. Because they leave plasma and distribute into tissues (and even adipose tissue), they are not confined to plasma, nor restricted to the liver, and they do cross membranes. Thus, the best description is that these drugs reach the brain very quickly due to easy membrane permeation.