What describes the journey of a drug from the bloodstream to its target cells?

The journey of a drug from the bloodstream to its target cells is best described as distribution. This process involves the movement of the drug through the circulatory system after it has been absorbed into the bloodstream. Once in circulation, the drug is transported to various tissues and organs, where it can interact with specific target cells to exert its therapeutic effects.

Distribution is influenced by several factors, including blood flow to the tissues, the drug's ability to cross cell membranes, and its binding to proteins in the plasma. Each of these factors plays a crucial role in determining how effectively the drug reaches its intended site of action.

In contrast, excretion refers to the elimination of the drug from the body, typically through urine or feces. Metabolism involves the biochemical alteration of the drug, primarily in the liver, which may affect its activity and distribution. Absorption is the process by which the drug enters the bloodstream after administration. While all these processes are integral to pharmacokinetics, distribution specifically addresses the pathway of the drug within the bloodstream to the target sites in the body.