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Chapter 1
Drugs/Agents and
Factors Affecting Their
Action
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
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

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

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Symptomatic treatment
Prevention
Diagnostic drugs
Curative
Health maintenance
Contraception
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Dosage Forms
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Tablets
Timed or sustained release
Tablets or controlled release
Capsule
Troches
Suppositories
(continues)
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(continued)
Dosage Forms

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Solutions
Douche
Suspensions
Emulsions
Topicals

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Patches
Drug implants
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Parenteral Product Packaging

Ampules

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Sterile
Sealed glass or plastic container
Contain a single liquid dose
Vials: either single or multiple dose

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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)

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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


Generic name


(+/-)-2-(p-isobutylphenyl) propionic acid
Ibuprofen
Trade name

Motrin
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U.S. Drug Legislation

Pure Food and Drug Act of 1906


Federal Food, Drug, and Cosmetic Act of
1938

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Required all drugs to meet minimal
standards
Required the drug to be safe before being
distributed over state lines
(continues)
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(continued)
U.S. Drug Legislation

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
Schedule I
High potential for
abuse
No medical use
Heroin
LSD
Schedule II
High potential for
abuse
Accepted medical
use
Morphine
Demerol
Schedule III
Lower potential for
abuse
Accepted medical
use
Librium, Valium,
hydrocodone,
Tylenol with codeine
Schedule IV
Lower potential for
abuse
Accepted medical
use
Librium
Valium
Schedule V
Lowest potential for
abuse
Accepted medical
use
Lomotil
Robitussin A-C
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Prescription Drugs
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Prescription drugs = legend drugs
Drugs prescribed by:
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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

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Referred to as a lock and key effect
(continues)
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(continued)
Drug receptor interaction. Binding with specific receptors
occurs only when the drug and its receptors have a
compatible chemical shape.
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(continues)
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(continued)
Principles of Drug Action
Receptors
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The better the fit, the stronger the drug’s
affinity, thus
Drug effect occurs at lower doses
(continues)
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(continued)
Principles of Drug Action
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Agonist effect
Antagonistic effect
Adverse drug effect
Therapeutic effect
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Pharmacokinetics: Absorption
Routes

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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


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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
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Kidneys (main organ)
Liver
Bowel
(continues)
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(continued)
Renal excretion of drugs. Note sites where
drugs are secreted and reabsorbed.
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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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