1. Pharmacologic Principles – Chapter 2
Names of drugs
Chemical
Trade
Generic
Phases of drug activity
Drug administered
Phase I – Pharmaceutical disintegration & dissolution
Drug available for absorption
Phase II – Pharmacokinetic – absorption, distribution, metabolism, excretion
Drug available for action
Phase III – Pharmacodyamic – drug receptor interaction
Effect
Pharmacotherapeutics
Type of therapy
Monitoring
Pharmacognosy
Toxicology
A drug is any chemical that affects the physiological process of a living organism. Pharmacology is the study of the science of drugs. Chemical name describes the drug’s chemical composition and molecular structure. Trade name is the drug owner’s registered trademark for the drug patent. Generic name is given to the drug by the USAN – United States Adopted Names Council. Drug’s have only one chemical name and generic name, however, once the patent expires the same drug can have many trade names. Pharmaceutics – how do the various forms of drugs (enteric, parenteral, topical) enter into and affect the body. Enteric coated tablets are absorbed slower than liquids, elixirs, and syrups. Enteric medications are broken down by the gastrointestinal enzymes and pH environments for absorption. Topical medications have one of two pharmaceutical effects – (1) working directly on the surface of the skin immediately and (2) the skin becomes a barrier that controls the release of the medication Parenteral medications should have a pH similar to the pH of blood. They have the most immediate effect on the body with 100% absorption. Pharmacokinetics – what is the drug’s onset, peak action, and duration. Occurs through the processes of absorption, distribution, metabolism, and excretion. Absorption is effected by the drug’s form (enteric, parenteral, topical). Distribution involves the transport of the drug by the circulatory system to the site of the intended action. Metabolism occurs primarily in the liver. Certain drugs may be metabolized by the skeletal muscle, kidneys, lungs, plasma, or intestinal mucosa. Cytochrome P-450 enzymes control the metabolism primarily of lipid-soluble, nonpolar drugs which are difficult for the body to eliminate. Excretion of the metabolized drug occurs primarily in the kidneys. A few drugs are excreted by the liver and the intestines. Renal excretion occurs through glomerular filtration, active tubular reabsorption, and active tubular secretion. The rate at which a drug is excreted from the body is called half-life. Amount of drug absorbed + amount of drug excreted is equal = called steady state. Onset = time when drug begins a therapeutic response; Peak = time when reaches maximum therapeutic response; Duration = total length of time the drug concentration has a therapeutic effect . Determined by a peak and trough laboratory test. Pharmacodynamics – how does the drug mechanically change living cells to produce a therapeutic or toxic effect. Mechanical changes occur through receptor interactions, enzyme interactions, and nonselective interactions. Receptor interactions take place in the protein structure of the targeted cell membrane producing either an agonist or antagonist effect. Enzyme interactions with a drug either inhibit (most common) or enhance (least common) a biochemical reaction within the cell. Nonselective interactions physically alter cell membranes or cell processes. These drugs are most often in the form of antibiotics or cancer drugs. Pharmacotherpeutics - includes the anticipated outcomes of the drug therapy, medication contraindications, adverse effects, therapeutic index, drug concentration, tolerance and dependence, drug interactions, additive effects, synergistic effects, antagonistic effects, incompatibility, adverse drug events, adverse drug reaction, allergic reaction, idiosyncratic reaction, pharmacogenetics, drug-induced teratogenesis. Pharmacognosy – plant, animal, mineral, and laboratory synthesis of drugs. Toxicology – adverse effects of chemicals
Every drug has one chemical and one generic name, but can have many trade names after the company’s patent expires. Drugs go through three phases of activity in the human body. Each stage has multiple functions to achieve a therapeutic effect for the patient. The nurse is responsible to know the type of drug therapy chosen and how to safely monitor the drug therapy. Drugs are made from many sources and have the potential to be toxic to the human body.