Download Chapter 1 - Drugs and Agents - Factors Affecting their Action

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

Study of the biochemical and physiological effects
of drugs
 Study of drugs’ mechanisms of action

Study of the absorption, distribution,
biotransformation (metabolism), and excretion of
drugs
 Four steps

Absorption
 Distribution
 Metabolism
 Excretion

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.

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

Study of poisons and poisonings
 All drugs have the potential to become toxic.


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

Drugs derived from:
Natural sources
 Semisynthetic sources
 Synthetic sources

Symptomatic treatment
 Prevention
 Diagnostic drugs
 Curative
 Health maintenance
 Contraception







Tablets
Timed or sustained release
Tablets or controlled release
Capsule
Troches
Suppositories
Solutions
 Douche
 Suspensions
 Emulsions
 Topicals



Patches
Drug implants

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


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


Chemical name


Generic name


(+/-)-2-(p-isobutylphenyl) propionic acid
Ibuprofen
Trade name

Motrin

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)

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
(continues)

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

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 Accepted medical
abuse
use
Librium, Valium,
hydrocodone,
Tylenol with
codeine
Schedule IV
Lower potential for Accepted medical
abuse
use
Librium
Valium
Schedule V
Lowest potential
for abuse
Lomotil
Robitussin A-C
Accepted medical
use
Prescription drugs = legend drugs
 Drugs prescribed by:







Physician
Nurse practitioner
Physician’s assistant
Dentist
Veterinarian
Others

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
Drug receptor interaction. Binding with specific receptors
occurs only when the drug and its receptors have a
compatible chemical shape.

Receptors
The better the fit, the stronger the drug’s affinity,
thus
 Drug effect occurs at lower doses

Agonist effect
 Antagonistic effect
 Adverse drug effect
 Therapeutic effect


Routes
Oral
 Parenteral
 Topical


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.

The transport of a drug in the body by the
bloodstream to its site of action

The elimination of drugs from the body
Kidneys (main organ)
 Liver
 Bowel

Renal excretion of drugs. Note sites where
drugs are secreted and reabsorbed.

Half-life

The time it takes for one half of the original amount
of a drug to be removed from the body