What does distribution refer to in pharmacology?

In pharmacology, distribution refers to the process by which a drug is transported from the bloodstream to various tissues and organs throughout the body after it has entered systemic circulation. This phase is essential as it determines the concentration of the drug at different sites of action, which in turn affects the drug's efficacy and potential side effects.

The factors that influence distribution include blood flow to various tissues, the ability of the drug to cross biological membranes, and the drug's solubility properties. The distribution phase plays a critical role in determining how effectively a drug can exert its therapeutic effects as well as how quickly it may reach a required concentration in the target tissues.

While the other options pertain to important pharmacological processes, they do not define distribution. One involves the initial transfer of the drug into the bloodstream, another discusses metabolic conversion, and the last focuses on how the drug is removed from the body. Each aspect contributes to the overall pharmacokinetic profile of a drug but the specific concept of distribution is most accurately encapsulated by delivering the drug to tissues throughout the body.