Drug Absorption and Distribution Practice Test

Tissue perfusion governs how quickly a drug moves from the blood into a given tissue. When blood flow to a tissue increases, more drug-laden blood arrives per unit time, so distribution to that tissue speeds up. When perfusion to a tissue drops, less drug reaches it and distribution slows. This effect is tissue-specific because different tissues receive different baseline blood flows; highly perfused organs like the liver, kidneys, and brain will show more pronounced changes in distribution with perfusion shifts than poorly perfused tissues such as adipose tissue. In pharmacokinetics, distribution can be perfusion-limited, meaning the rate at which the drug leaves plasma and enters tissue is constrained by blood flow, so changing perfusion directly alters how fast equilibrium between plasma and tissue is achieved. Therefore, changes in perfusion can speed up or slow distribution to specific tissues depending on the perfusion changes.