Chapter 1
Basic Principles of Pharmacology
Clayton’s Basic Pharmacology for Nurses,
20th edition
Michelle J. Willihnganz, MS, RN, CNE
Learning Objectives
(1 of 2)
Identify the various methods used to classify drugs.
2. Discuss the difference between prescription drugs,
nonprescription drugs, and dietary supplements.
3. Identify available drug information sources.
4. Describe the five classifications or schedules that are
outlined in the Controlled Substances Act.
5. Describe the process of developing and bringing new
drugs to market.
1.
Learning Objectives
(2 of 2)
Identify common drug administration routes.
6. Describe the process of how a drug is metabolized in
the body.
7. Compare and contrast the following terms that are
used in relationship to medications: desired action,
common adverse effects, serious adverse effects,
allergic reactions, and idiosyncratic reactions.
8. Identify drug interactions by differentiating among the
terms additive effect, synergistic effect, antagonistic
effect, displacement, interference, and
incompatibility.
5.
Lesson 1.1
Basic Principles of Pharmacology
Foundations of Pharmacology
(1 of 3)
Pharmacology deals with the study of drugs
and their actions or effects
From Greek words pharmakon and logos
Physiotherapy uses water, light, and heat
Psychotherapy identifies stressors and
methods used to reduce them
Foundations of Pharmacology
(2 of 3)
Therapeutic methods are approaches to
treating illnesses
➢ Diet therapy
➢ Drug therapy
➢ Physiotherapy
➢ Psychotherapy
Therapeutic methods are often used in
combination
Foundations of Pharmacology
(3 of 3)
Biologic therapy: A new class of drugs; has
transformed treatment of patients with
disorders that attack the body’s own organs,
tissues, and cells
Biologic agents are large, complex proteins
manufactured in a living system
Chemical Name
Most meaningful to the chemist
Chemist understands the exact chemical
constitution of the drug and the exact
placement of its atoms or molecular
groupings
Generic and Brand Names
Generic name: Important to know because
formularies use them; not capitalized
Official name: Listed by FDA
Brand or trademark: Registered by
manufacturer; capitalized
Audience Response Question 1
Which name(s) of a drug should the nurse
use when teaching a patient about a new
prescription?
a) Trade
b) Generic and trade
c) Generic and chemical
d) Official
Drug Classifications
Body system classification (e.g.,
cardiovascular, gastrointestinal)
Therapeutic use or clinical indications (e.g.,
antacids, antibiotics)
Physiologic or chemical action (e.g.,
anticholinergics, calcium channel blockers)
Further Classifications
Prescription: Requires an order by a health
professional licensed to prescribe drugs
Nonprescription: Over-the-counter (OTC)
drugs sold without a prescription
Illegal or recreational drugs: Used for
nontherapeutic purposes; obtained illegally
Biosimilar: Biologic product that is close in
structure/function to an existing approved
biologic product
Resources for Drug Information
Official source for American drug standards
➢ The United States Pharmacopeia (USP)/National
Formulary (NF)
➢ USP Dictionary of USAN and International Drug
Names
Sources for prescription and nonprescription
drugs
➢ Package inserts
➢ Nursing journals
➢ Electronic databases
Audience Response Question 2
Which source of information is best for the
nurse to obtain drug information?
Physicians’ Desk Reference (PDR)
b) Nursing journals
c) United States Pharmacopeia (USP) and National
Formulary (NF)
d) Electronic databases
a)
Common Sources of Drug
Information
Electronic databases
➢ Cumulative Index of Nursing and Allied Health
(CINAHL)
➢ Lexicomp
➢ ePocrates
➢ DailyMed
United States Drug Legislation
Federal Food, Drug, and Cosmetic Act (1938,
1951, 1962)
Controlled Substances Act (1970): Defined
five classifications or schedules of controlled
substances
➢ Schedule I
➢ Schedule II
➢ Schedule III
➢ Schedule IV
➢ Schedule V
Audience Response Question 3
Which entity is responsible for monitoring
drug safety in the United States?
a) Drug Enforcement Agency (DEA)
b) Department of Justice (DOJ)
c) U.S. Food and Drug Administration (FDA)
d) World Health Organization (WHO)
Audience Response Question 4
Which drug schedule indicates drugs with the
highest risk for abuse?
Schedule I
b) Schedule II
c) Schedule III
d) Schedule IV
e) Schedule V
a)
Controlled Substances
(1 of 2)
Manufacturers, prescribers, and dispensers
must register with the DEA: Requirements
must be met to dispense scheduled
medications
Controlled substances in hospitals: Inventory
and dispersion control records
Controlled Substances
(2 of 2)
Possession of controlled substances by
individuals: Nurses may not have controlled
substances in their possession
Effectiveness of drug legislation: Enforcing
laws regarding the proper distribution and use
of drugs is dependent on many organizations
working together to ensure understanding of
reasons for drug legislation
New Drug Development
Rules and regulations evolved by FDA divide
into four stages
➢ Preclinical research and development: Average
time is 18 months
➢ Clinical research and development: May require 2
to 10 years; average is 5 years
➢ New Drug Application (NDA) review: Average time
is 17 months
➢ Postmarketing surveillance
Tracking
Fast tracking: Used to expedite drug
development and approval for life-threatening
illnesses
Parallel tracking: Used for patients with lifethreatening illnesses who cannot participate
in controlled trials, when there is no other
alternative
Postmarketing Surveillance
Stage
Ongoing review of adverse effects of new
drugs
Black box warning
➢ Indicates a very serious life-threatening problem
➢ Probability of a drug acquiring a new black box
warning or being withdrawn from the market within
25 years of being released is 20%
Rare Diseases and the
Development of Orphan Drugs
National Organization for Rare Disorders
estimates that 6000 rare health conditions
exist in about 20 million Americans
Orphan drugs: Medicines developed for rare
disorders
Orphan Drug Act, 1983: Promotes
development of products that demonstrate
promise for diagnosis or treatment of rare
diseases or conditions
Audience Response Question 5
How many years on average does it take for
a drug to be brought to market from the time
of its conception?
a) 2 to 3
b) 4 to 7
c) 8 to 15
d) 12 to 18
Drug Responses in the Body
Drug receptors: Specific sites where drugs
form chemical bonds
Pharmacodynamics: Study of interactions
between drugs and their receptors and the
series of events that result in a
pharmacologic response
Agonists: Drugs that interact with a receptor
to stimulate a response
Antagonist: Drugs that attach to a receptor
but do not stimulate a response
Routes of Drug Administration
Enteral: Via the gastrointestinal tract by the
oral, rectal, or nasogastric routes
Parenteral: Bypasses the GI tract by using
subcutaneous, intramuscular, and
intravenous injection
Percutaneous: Absorbed through the skin
and mucous membranes
➢ Inhalation, sublingual, or topical
Drug Stages After Administration
LADME
➢ Liberation: Drug released from dosage form
➢ Absorption: Depends on route of administration
➢ Distribution: Depends on circulation to be
transported throughout body
➢ Metabolism: Depends on enzyme systems
➢ Excretion: Depends on GI tract and kidneys
Liberation
Drug released from dosage form and is
dissolved in body fluid
Process of converting oral drug can be
influenced by food and water in the stomach
Audience Response Question 6
All drugs are processed in the body through
pharmacokinetics. What is the correct order
that drugs pass through the body?
a) Liberation, absorption, distribution, metabolism,
excretion
b) Distribution, metabolism, liberation, absorption,
excretion
c) Biotransformation, liberation, distribution,
absorption, excretion
d) Excretion, distribution, liberation, absorption,
metabolism
Absorption
Drug is transferred from entry site into the
body’s circulating fluids
Absorption rate depends on route, blood flow,
and solubility of the drug
Subcutaneous and intramuscular injection
absorption is affected by circulation
Intravenous medications are absorbed fastest
Topical medications applied to the skin can
be influenced by skin thickness and hydration
Audience Response Question 7
Which route of administration has the fastest
rate of distribution?
a) Subcutaneous
b) Intramuscular
c) Transcutaneous
d) Intravenous
Distribution
Drugs are transported throughout the body by
body fluids to the sites of action
➢ Protein binding and fat solubility affect distribution
Organs with largest blood supply receive the
distributed drug most rapidly
Some drugs cannot pass through the bloodbrain barrier or the placental barrier
Metabolism
The process whereby the body inactivates
drugs
Primary organ of metabolism is the liver;
other sites are GI tract and lungs
Excretion
Elimination of drug metabolites and some of
the active drug from the body
Kidneys are the major organ of excretion;
some excreted in feces
Half-Life of Drugs
Factors modifying the quantity of drug
reaching a site of action after a single oral
dose
Audience Response Question 8
When the nurse administers a 50-mg dose of
a drug with a half-life of 6 hours, how many
milligrams will remain in the body at 24
hours?
a) 25 mg
b) 12.5 mg
c) 6.25 mg
d) 3.13 mg
e) 1.56 mg
Drug Actions
Onset of action: When the concentration of a
drug at the site of action is sufficient to start a
physiologic response
Peak action: Time at which the drug reaches
the highest concentrations on the target
receptor sites
Duration of action: How long the drug has a
pharmacologic effect
Drug Blood Level
When a drug is circulating in the blood, a
blood sample may be drawn and assayed to
determine amount of drug present
Important for certain drugs, like
anticonvulsants
If drug blood level is low, dosage may be
increased; if it is high, dosage must be
reduced
Adverse Effects of Drugs
Desired action
Side effects
Adverse effects (common and serious)
Idiosyncratic reactions: Occur when
something unusual/abnormal happens when
drug is first administered
Allergic reactions: Occur among patients who
have previously been exposed to a drug and
whose immune systems have developed
antibodies to the drug
Audience Response Question 9
A patient is being started on a new drug that
has been used safely by many people for
years. The patient has no known allergies,
and the nurse administers the drug correctly.
Suddenly the patient experiences cardiac
arrest. What is this type of reaction called?
a) Allergic
b) Mutagenic
c) Idiosyncratic
d) Therapeutic
Drug Interactions
Said to occur when the action of one drug is
altered or changed by the action of another
drug
Elicited in the following two ways:
➢ By agents that, when combined, increase the
action of one or both drugs
➢ By agents that, when combined, decrease the
effectiveness of one or both drugs
Changes in Absorption
Most drug interactions that alter absorption
take place in the GI tract
➢ Antacids increase the gastric pH and can inhibit
the dissolution of ketoconazole tablets
Many alterations in absorption can be
managed by separating the times of
administration
Changes in Distribution
(1 of 2)
Many interactions that cause a change in
distribution usually affect the binding of a
drug to an inactive site
Unbound drugs: Pharmacologically active
portion
Drugs are “bound” to proteins in the blood
during transportation
Changes in Distribution
(2 of 2)
The more a drug is bound to a protein, the
less available it is to the circulation
Some medications can cause binding or
unbinding of another medication, increasing
or decreasing its effect
Changes in Metabolism
Drug interactions usually result from a
change in metabolism that involves inhibiting
or inducing the enzymes that metabolize a
drug
Serum drug levels usually increase a result of
inhibited metabolism when drugs are given
concurrently
Changes in Excretion
Drug interactions that cause a change in
excretion usually act in the kidney tubules by
changing the pH to enhance or inhibit
excretion
Drug Interaction
Additive effect
Synergistic effect
Antagonistic effect
Displacement
Interference
Incompatibility
Audience Response Question 10
A patient reports postoperative pain, and the
nurse administers IV morphine (a narcotic
analgesic) to ease the pain. Fifteen minutes
later, the nurse notes that the patient is very
drowsy, respirations are slow and shallow,
and oxygen saturation is low. The nurse
administers another drug that decreases the
morphine’s action. What is this effect called?
a) Displacement
b) Antagonistic
c) Interference
d) Synergistic
0
