What is one potential effect of the blood-brain barrier on drug distribution in the elderly?

The blood-brain barrier (BBB) is a selective permeable barrier that protects the brain from potentially harmful substances in the bloodstream while allowing essential nutrients to pass through. In elderly individuals, changes in the physiology of the BBB can significantly impact how drugs are distributed to the brain.

As people age, the integrity of the BBB may become compromised, which can lead to alterations in its permeability. This can result in less effective passage of certain drugs across the barrier. Additionally, the age-related decline in various physiological functions, such as reduced cerebral blood flow and changes in brain composition, may further affect drug delivery to the central nervous system. Thus, the correct answer highlights that the effect of the blood-brain barrier in the elderly can result in less efficient drug transport, leading to potential challenges in achieving the desired therapeutic effects of medications that target the brain.