Which term describes the transport of a drug through the bloodstream to its site of action?

The correct answer is distribution. This term refers to the process by which a drug is transported through the bloodstream to its target tissues or sites of action after it has been administered. Once a medication enters the body, it is absorbed into the bloodstream, and then distribution occurs as the drug circulates throughout the body. Factors affecting drug distribution include blood flow to tissues, the ability of the drug to cross cell membranes, and the binding of drugs to plasma proteins.

In the context of pharmacology, understanding distribution is crucial because it influences the drug's effectiveness and the duration of its effects in the body. A drug may be well absorbed but if it is not distributed adequately to the target site, its therapeutic effects may be diminished.

The other terms pertain to different processes: metabolism involves the chemical alteration of the drug, absorption refers to the process of taking the drug into the body from its site of administration, and excretion is the elimination of the drug from the body. Each of these processes is integral to pharmacokinetics, but when discussing the transport of a drug specifically to its site of action within the bloodstream, distribution is the most accurate descriptor.