In pharmacokinetics, distribution occurs primarily through which system?

• A. Lymphatic system
• B. Circulatory system
• C. Digestive system
• D. Nervous system

Answer: (B)

The distribution phase is about how a drug moves from the bloodstream into tissues, and it happens primarily through the circulatory system. After absorption, the drug rides in the blood and reaches organs according to blood flow to those tissues. How widely and quickly it distributes depends on factors like how well the drug crosses capillary walls, how its molecules permeate cell membranes, and how much of the drug binds to plasma proteins (which can keep some of it in the blood and limit distribution). The lymphatic system does play a role for certain substances, especially some fat-soluble compounds, but for most drugs the bloodstream is the main delivery route.