chapter 1 drugs/agents and factors affecting their action
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Chapter 1
Drugs/Agents and Factors Affecting Their Action
Copyright 2007 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.
Pharmacology
Study of the history, sources, and physical and chemical properties of drugs
Also looks at the ways in which drugs affect living systems
Various subdivisions of pharmacology have evolved
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Pharmacodynamics
Study of the biochemical and physiological effects of drugs
Study of drugs’ mechanisms of action
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Pharmacokinetics
Study of the absorption, distribution, biotransformation (metabolism), and excretion of drugs
Four steps Absorption Distribution Metabolism Excretion
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Pharmacotherapeutics
Study of how drugs may best be used in the treatment of illnesses
Study of which drug would be most appropriate or least appropriate to use for a specific disease; what dose would be required; etc.
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Pharmacognosy
The study of drugs derived from herbal and other natural (plant and animal) drug sources
Studying compositions of natural substances helps to gain knowledge for developing synthetic versions
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Toxicology
Study of poisons and poisonings All drugs have the potential to become
toxic.
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History of Pharmacology
Ancient Egypt: the cradle of pharmacology
These medical sources listed over 700 different remedies for different ailments.
First century: Dioscorides prepared De Materia Medica:
Listed and classified 600 different plants used for medicinal purposes; first time plants were ever classified
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Sources of Drugs
Drugs derived from: Natural sources Semisynthetic sources Synthetic sources
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Drug Uses
Symptomatic treatment Prevention Diagnostic drugs Curative Health maintenance Contraception
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Dosage Forms
Tablets Timed or sustained release Tablets or controlled release Capsule Troches Suppositories
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Dosage Forms
Solutions Douche Suspensions Emulsions Topicals
Patches Drug implants
(continued)
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Parenteral Product Packaging
Ampules Sterile Sealed glass or plastic container Contain a single liquid dose
Vials: either single or multiple dose Glass or plastic container Sterile liquid dose Sealed with a rubber diaphragm
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Drug Names
Chemical name The drug’s chemical composition and
molecular structure Generic name (nonproprietary name)
Name given by the United States Adopted Names Council
Allows the drug to be marketed
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Brand Name
Also called trade name (proprietary name)
The drug has a registered trademark; use of the name is restricted by the drug’s owner
(usually the manufacturer) Allows the drug to be commercially
distributed The superscript ® is registered by the U.S.
Patent Office and approved by the FDA (Food and Drug Administration)
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Drug Names: Examples
Chemical name (+/-)-2-(p-isobutylphenyl) propionic acid
Generic name Ibuprofen
Trade name Motrin
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U.S. Drug Legislation
(continues)
Pure Food and Drug Act of 1906 Required all drugs to meet minimal
standards Federal Food, Drug, and Cosmetic Act of
1938 Required the drug to be safe before being
distributed over state lines
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U.S. Drug Legislation(continued)
1970: Comprehensive Drug Abuse Prevention and Control Act
Also known as Controlled Substance Act: classified drugs according to their abuse potential
Regulates the manufacture and distribution of drugs causing dependence
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Controlled Substances Schedules
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Schedule I High potential for abuse
No medical use HeroinLSD
Schedule II High potential for abuse
Accepted medical use
MorphineDemerol
Schedule III Lower potential for abuse
Accepted medical use
Librium, Valium, hydrocodone, Tylenol with codeine
Schedule IV Lower potential for abuse
Accepted medical use
LibriumValium
Schedule V Lowest potential for abuse
Accepted medical use
LomotilRobitussin A-C
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Prescription Drugs
Prescription drugs = legend drugs Drugs prescribed by:
Physician Nurse practitioner Physician’s assistant Dentist Veterinarian Others
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Principles of Drug Action
Drugs Alter existing cellular or chemical functions Exert their action by forming a chemical
bond with specific receptors within the body Referred to as a lock and key effect
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Drug receptor interaction. Binding with specific receptors occurs only when the drug and its receptors have a compatible chemical
shape.
(continued)
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Principles of Drug Action
(continues)
Receptors The better the fit, the stronger the drug’s
affinity, thus Drug effect occurs at lower doses
(continued)
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Principles of Drug Action
Agonist effect Antagonistic effect Adverse drug effect Therapeutic effect
(continued)
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Pharmacokinetics: Absorption
Routes Oral Parenteral Topical
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Metabolism: First-Pass Effect
The metabolism of a drug and its passage from the liver into the circulation
Metabolism occurs in the liver Liver enzymes react with the drug Increases the dosage requirement
The same drug—given IV—bypasses the liver, preventing the first-pass effect from taking place, and more drug reaches the circulation.
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Pharmacokinetics: Distribution
The transport of a drug in the body by the bloodstream to its site of action
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Elimination/Excretion
The elimination of drugs from the body Kidneys (main organ) Liver Bowel
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Renal excretion of drugs. Note sites where drugs are secreted and
reabsorbed.
(continued)
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Copyright 2007 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.
Pharmacokinetics:Measuring Drug Action
Half-life The time it takes for one half of the original
amount of a drug to be removed from the body
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