Drugs and Factors Affecting Their Action Chapter 1
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History of Pharmacology Plants original pharmacy Egypt: ancient
remedies from over 3,000 years ago Hippocrates: natural laws to
understand health and disease Various other scientists studied
throughout the centuries We now have thousands of drugs available
with more being developed all the time
Pharmacology Study of the history, sources, and physical and
chemical properties of drugs 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,
metabolism, and excretion of drugs This is drug card info
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Pharmacotherapeutics Study of how drugs may best be used in the
treatment of illnesses Which drug would be most appropriate to use
for a specific disease at what dose, etc.
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Pharmacognosy 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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Sources of Drugs Natural Semisynthetic Synthetic
Biotechnology
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Drug Uses Treatment of symptoms (pain relievers) Preventative
drugs (vaccines) Diagnostic drugs (dyes) Cure (antibiotics) Health
maintenance (insulin) Contraceptives (birth control)
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Dosage Forms Tablets Time released tablets Capsules (useful for
liquids) Troches or lozenges Suppositories Solutions Suspensions
Emulsions Topicals Implants Parenteral products
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Common medication routes Intravenous or IV injected into a vein
Intramuscular or IM injected into a muscle Intradermal injected
under the skin Subcutaneous or SQ injected into fatty tissue Oral
or PO by mouth
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U.S. Drug Legislation 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 Comprehensive Drug Abuse Prevention and
Control Act 1970 - Also known as Controlled Substance Act which
classified drugs according to their abuse potential - Regulates the
manufacture and distribution of drugs causing dependence
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Controlled substances schedule Schedule IHigh abuse potential
No medical useHeroin, LSD Schedule IIHigh abuse potential Accepted
medical use Morphine Demerol Schedule IIILower abuse potential
Accepted medical use Vicodin Tylenol/codeine Schedule IVLower abuse
potential Accepted medical use Librium Valium Schedule VLowest
abuse potential Accepted medical use Lomotil Robitussin AC Schedule
VI (some states) Definite abuse potential Accepted medical use some
states Marijuana is only drug in this category
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Drug Classification As a result of legislation, four general
drug categories were identified: 1. Prescription drugs 2.
Non-prescription drugs (over the counter or OTC) 3. Investigational
drugs - Drugs being tested under the FDA 4. Illicit or street
drugs
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Drug Information Resources The Physicians Desk Reference (PDR)
The American Drug Index Drug Facts and Comparisons The Handbook of
Non-prescription Drugs Drug Interactions The Product Insert The
Pharmacist Nursing Drug Guides Formulary
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Physicians Desk Reference (PDR) An annual publication
containing several types of drug information including appearance
and chemical properties of drugs. Primarily used by prescribers
(physicians, nurse practitioners, etc.) The PDR can be a good
reference book, but it does not provide nursing implications.
Nurses may find that specific nursing drug guides are more helpful
for everyday use.
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The Product Insert A detailed description Approved by the FDA
Categories - Brand name - Generic name - Description - Clinical
Pharmacology - Contraindications - Warnings - Precautions - Over
dosage - Dosage and administration - How supplied
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Drug Names Chemical name - The drugs chemical composition and
molecular structure Generic name (non-proprietary name) - Name
given by the United States Adopted Names Council - Allows the drug
to be marketed
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Drug Names Brand name - Also called trade name (proprietary
name) - The drug has a registered trademark; use of the name is
restricted by the drugs owner (usually the manufacturer) for life
of patent usually 17 years - Allows the drug to be commercially
distributed - The superscript is registered by the U.S. Patent
Office and approved by the Food and Drug Administration (FDA)
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Examples of Drug Names Chemical name (+/-)-2-(p-isobutylphenyl)
propionic acid Generic name Ibuprofen Trade or Brand name Motrin or
Advil
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Principles of Drug Action Drugs alter existing cellular or
chemical functions Some drugs exert their action by forming a
chemical bond with specific receptors within the body referred to
as a lock and key effect - Agonists: substance that interacts with
receptor to produce response - Antagonists: substance preventing
action of agonist
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Principles of Drug Action Receptors - The better the fit, the
stronger the drugs affinity; therefore, the drugs effect occurs at
lower doses
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Principles of Drug Action Primary effect - Desired or
therapeutic effect of the medication Secondary effect - All other
effects produced by the drug, whether desirable or undesirable
example: Compazines primary effect is anti-emetic. Secondary effect
is anti- psychotic
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Liberation Oral administration may require full glass of fluid
to aid administration Dissolves in the gastric or intestinal
fluids
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Absorption First step in the passage of a drug into the body
(bloodstream) Absorption can be faster when drug is consumed with
fluids as it increases rate of dissolution Presence of food may
slow absorption Most drugs are absorbed in the small intestine
Bioavailability describes absorption efficiency
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Distribution The transport of a drug in the body by the
bloodstream to its site of action
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Metabolism Occurs before excretion and makes drugs water
soluble to be able to pass through the kidneys Also called
biotransformation Metabolism occurs in the liver where liver
enzymes react with the drug
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Elimination/Excretion The elimination of drugs from the body -
Kidneys (primary organ for excretion) - Liver - Bowel
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Adverse Drug Reaction (ADR) ADR is the term used to describe
unwanted, negative consequences associated with the use of a
medication Alternative terms are side effect and adverse
effect
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Types of ADRs Allergic Reactions - Type of unpredictable ADR -
Response of the Patients immune system to the presence of the drug
- Does not occur unless the patient has been previously exposed to
the drug - Response may range from mild (rash) to life threatening
(anaphylaxis)
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Types of ADRs Drug Idiosyncrasy - Abnormal reactivity to a drug
caused by genetic differences can occur on first exposure Drug
Tolerance - Patient requires a higher dosage or more frequent
administration for a therapeutic effect
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Types of ADRs Toxic Reactions - Related to dosage administered
- All drugs have the capability of producing a toxic effect
Teratogenic Effect - Drug causes congenital defects usually in
first trimester
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Common Lab Tests to Measure Drug Action Therapeutic levels
Tests based on what the drug is supposed to do Examples: CBC for
antibiotics or PTT for Coumadin, peak/trough for antibiotics
(gentamicin)
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Pharmacokinetics Half life - The time it takes for one half of
the original amount of a drug to be excreted from the body Used to
maintain drug levels over a 24 hour period
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Factors Influencing Drug Response Age Weight Gender Disease
Route of Administration
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Drug Interactions Drug-drug interaction occurs when the effects
of one drug are potentiated or diminished by another drug -
Example: Antacids diminish the effect of tetracycline Drug-food
interaction occurs when a specific food ingested increases or
decreases the effect of a drug - Example: Grapefruit juice
increases effects of calcium channel blockers
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Drug Incompatibilities Drugs are chemical compounds Can
interact with each other Most often an issue in parenteral
administration when mixing solutions Must always determine the
safety of mixing solutions before giving to patients When in doubt,
give separately
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Herbals and Botanicals Herbs are used by 80% of the world
population Sold in nutrition stores, major drug chains, and
discount retail stores (even supermarkets) Herbals are not
regulated by the FDA Herbals are chemicals Must assess patients use
of these products as some can have interactions with prescription
drugs