Pharmacology Principles

Abstract

It is important for anesthesia providers to understand basic pharmacology principles in order to administer anesthetic medications safely and effectively. These principles include pharmacokinetics (what happens to a drug after it is administered) and pharmacodynamics (the effect of the drug on the patient’s body).

Pharmacokinetics is generally divided into stages of absorption, distribution, metabolism, and excretion. Major factors to consider with drug absorption include the route of administration of a drug, the potential for first-pass metabolism by the liver, and the effect of ionization on the drug’s absorption. Distribution of a drug involves the drug’s free fraction and protein binding, volume of distribution and potential for redistribution, and the potential for storage of the drug in body tissues. Metabolism of drugs involves consideration of the organs involved in drug breakdown, as well as the kinetics of a drug’s metabolism and excretion.

Pharmacodynamics involves understanding a drug’s potency, efficacy, toxicity, and therapeutic index. It is also important to understand a drug’s actions on cellular receptor systems. In the case of antagonist drugs, competitive versus non-competitive antagonism is a key concept to recognize. For agonistic drugs, it is essential to understand the concepts of additive and synergistic responses.