Pharmacokinetics is about how drugs move around the body, being absorbed, distributed to their sites of action, and being eliminated. Pharmacodynamics is about all those matters that are concerned with the pharmacological actions of drugs when they get to their sites of action, whether they be determinants of beneficial or adverse effects.
Below is a link to Chapter 1 of Jeffrey Aronson’s new guide to Clinical Pharmacology. Cite as Aronson J (2016): Pharmacodynamics: How Drugs Work. DOI: 10.13140/RG.2.1.4857.9446
Pharmacodynamics – How Drugs Work