Which statement best describes pharmacodynamics?

Pharmacodynamics is the branch of pharmacology that studies the effects of drugs on biological systems and the mechanisms of action. When we say that pharmacodynamics examines how drugs affect the body, we are referring to the interactions between the drug and its target sites, such as receptors, enzymes, or cellular pathways. This includes understanding both the therapeutic effects and potential side effects of a drug.

In contrast to this concept, drug absorption, distribution, and excretion are all facets of pharmacokinetics, which focuses on how the body affects a drug over time concerning the processes of absorption, distribution, metabolism, and elimination. Therefore, while absorption and distribution describe how the body handles a drug, they do not encompass the fundamental purpose of pharmacodynamics, which directly relates to a drug's action and effect within the body.