There is an emerging need for greater understanding of pharmacology principles among technical staff. Indeed, the responsibility of dose preparation and administration, under any level of supervision, demands a foundational understanding of pharmacology. This is true for radiopharmaceuticals, contrast media, and pharmaceutical interventions or adjunctive medications. Regulation around the same might suggest a need to embed pharmacology theory in undergraduate education programs, and there is a need to disseminate that same foundational understanding to practicing clinicians. Moreover, pharmacology foundations can provide a key understanding of the principles that underpin quantitative techniques (e.g., pharmacokinetics). This article is the first in a series that aims to enhance the understanding of pharmacologic principles relevant to nuclear medicine. This article will deal with the introductory concepts, terminology, and principles that underpin the concepts to be discussed in the remainder of the series. The second article will build on the pharmacodynamic principles examined in this article with a treatment of pharmacokinetics. Article 3 will outline pharmacology relevant to pharmaceutical interventions and adjunctive medications used in general nuclear medicine, article 4 will cover pharmacology relevant to pharmaceutical interventions and adjunctive medications used in nuclear cardiology, and article 5 will discuss the pharmacology related to contrast media associated with CT and MRI. The final article (6) in the series will examine the pharmacology of drugs associated with the crash cart/emergency trolley.