Introduction and Definitions of Pharmacodynamics – Pharmacodynamics

Welcome to pharmacology by Lecturio. Today's topic is pharmacodynamics. We are going to evaluate and see how drugs move through the body in pharmacodynamics. Let's go over a couple of definitions. Excretion is the physical removal of drug from the body. So for example, we're excreting drug into the urine, or into the bile, or exhaling inhalational drugs. Elimination is a biochemical process without actual removal. So, eliminating a drug means that the drug may still be in the body, but you've rendered it somehow different through a biochemical process. A receptor is a specific protein on or in the cell that binds to the drug to effect the change. And effectors are molecules that effect a change as a result of the receptor and drug binding together. So, a receptor binds to the drug, and effector molecule goes and does the job of the drug. Affinity refers to the strength of the bond between a drug and receptor. And selectivity refers to the proportion of or a preference of a receptor has for a particular drug. It's usually compared to another similar kind of receptor, for example, we may have selectivity for the alpha 1 receptor versus the alpha 2 receptor, and the selectivity ratio may be 1000:1. Specificity refers to the amount of preference a receptor has for a particular drug. So, it's usually thought of as a comparator to another drug. So for example, one drug might be more specific to a receptor than a second drug. Agonism refers to the ability to activate the mechanisms to cause an effect. And antagonism is the ability to inhibit the mechanism to cause a biologic effect. Efficacy refers to the maximum effect of a drug at its highest tolerated dose. Well, potency is a measurement of the amount of...