Transcript Introduction to Pharmacology NAPNES Guidelines

Catherine Luksic BSN, RN
Level I
 DRUG

Any chemical that affects the physiologic processes of a
living organism
 PHARMACOLOGY


Study (science) of drugs
Includes:
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Absorption
Distribution
Metabolism
Excretion
Mechanism of Action
Therapeutic effects
Adverse effects
 Subspecialty
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Areas of Pharmacology
Pharmaceutics
Pharmacokinetics
Pharmacodynamics
Pharmacotherapeutics
Pharmacognosy
Toxicology
NURSES MUST UNDERSTAND BASIC PRINCIPLES OF
PHARMACOLOGY


Therapeutic and Toxic
SAFETY !
 Drugs
will acquire 3 names
 CHEMICAL (N-4 hydroxyphenyl acetamide)

Drugs chemical composition, molecular structure
 GENERIC


Shorter than chemical name
Used as official listing of drugs
 TRADE


(acetaminophen)
(Tylenol)
Registered trademark, “brand” name
Name is restricted to “owner” (company, ie, Merck)
**Patent lasts 17 years
- 10 years for research and development
- 7 years of marketability
 Process
of turning chemicals into safe
medications
 Science


of dosage form & design
ie – tablet, capsule, liquid, powder, etc.
Study of how various dosage forms/designs
influence a drugs metabolism and use in the body
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Design that will allow drug molecules to bind
to a target site
 Drug
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Oral
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Intramuscular, Subcutaneous, Intravenous,
Topical
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Via intestine
Via NG tube, feeding tube (or rectal)
Rectal
Parenteral
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Via mouth
Includes sublingual, buccal
Enteral
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
routes
Directly applied to skin
Mucosal
**Forms/designs of drugs:
 Oral
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Tablets, capsules, powder, liquid, elixir, suspension
EC, ER, SR
 Enteral
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Meds given via NG or feeding tube (solid or liquid)
Crushed meds – must be dissolved
 Rectal
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Suppositories, creams, enema
Also considered as ENTERAL route
 Parenteral
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Injections (solutions, powder)
 Topical
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Ointments, creams, pastes, powders, patches
 Mucosal
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eye, ear, nasal, vaginal
 Inhaled
Drug
Dissolution & Absorption
**Drugs must dissolve 1st (before absorbed)
Oral
Preparations
Liquids, elixirs, syrups
Suspension solutions
Powders
Capsules
Tablets
Enteric coated tablets
Extended release tablets
Fastest
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Slowest
*Extended Release (forms) = SR (slow release), CR
(controlled release), XL (extended length)
Drug
Dissolution & Absorption
 Parenteral Preparations
Do
NOT have to dissolve 1st
Subcutaneous,
Intramuscular
Intravenous
*directly into bloodstream
*immediate absorption
 Study
of what happens to a drug from
entrance into body until it leaves the
body
4
phases
 Absorption
 Distribution
 Metabolism
 Excretion
 Absorption
 Occurs
after dissolution of drug
 Drug → GI tract → blood/body fluids →
tissue
 Affected by form of drug
 Affected by ROUTE of administration
(oral, parenteral,etc.)
Factors That Affect Absorption
 Administration
route
 Dosage formulation
 Food or fluids administered with the drug

Grapefruit, fruit juices, antacids, fat soluble vitamins, iron
 Rate
of blood flow to the small intestine
 Acidity of the stomach
 Status of GI motility
 Bioavailability
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Extent of drug absorption
Amount of drug actually available to circulation
Depends upon “first pass effect”
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Example: Aspirin
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Has high “first pass effect”
 First
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Drugs must dissolve & be absorbed by GI tract
Must pass through LIVER before reaching
circulation (bloodstream)
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Pass effect
Drug
GI system
Portal vein
Liver
Hepatic vein
Circulation (distribution)
Liver may metabolize drug into smaller
metabolites
Therefore, less amount of drug will pass into
circulation
Intravenous drugs = no “first pass” in liver
Oral/Enteral Route
 Drug is absorbed into the systemic circulation
through the oral or gastric mucosa, the small intestine,
or rectum
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Oral – high “first pass” effect
Sublingual – dissolve under tongue, highly vascular area,
these drugs bypass liver, no “first pass” effect
Buccal – same as sublingual
Rectal (suppository or topical) – rectal drugs have SOME
“first pass” effect
 Routes
that bypass the liver:
 Sublingual
 Buccal
 Rectal*
 Intravenous
 Intranasal
Transdermal
Vaginal
Intramuscular
Subcutaneous
Inhalation
*Rectal drugs may have some degree of first-pass effect
Parenteral Route
*No “first pass” effect
 Intravenous*
 Intramuscular
 Subcutaneous
 Intradermal
 Intraarticular (physician)
*Fastest delivery into the blood circulation
Topical/Mucosal Route

Skin

Includes transdermal route, patches
Eyes
 Ears
 Nose
 Vagina

Topicals = slower onset, longer duration
 No “first pass” effect, bypass liver
 Exception = rectal
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 Transport
of drug by bloodstream to site of
action
 Areas of “rapid” distribution
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Heart
Liver
Kidneys
Brain
 Areas of
 Muscle
 Skin
 Fat
“slower” distribution
 Areas “difficult” to reach
 Bone
 Blood brain barrier **
 BLOOD

BRAIN BARRIER
Restricts passage of various chemicals between
the bloodstream and the central nervous
system
 CNS = brain, spinal cord
 BBB
 allows
 may
oxygen to pass
restrict certain bacteria & viruses
 Not all meds can pass through
 Distribution
depends upon protein-binding
 Albumin = most common blood protein,
carries protein-bound drug molecules
 “bound” portion of drug = pharmacologically
inactive
 “unbound” portion = pharmacologically
active

Easily distribute to body tissues (outside of blood
vessels) and reach site of action
 Lasix,
Coumadin, Aspirin, Digoxin
 aka
“Biotransformation”
 Process by which a drug is biochemically
altered
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inactive metabolite (compound)
more potent, active metabolite
Less potent, active metabolite
 LIVER
– most responsible for metabolism of
drugs
 Also involved = kidneys, lungs, skeletal
muscle, intestines
Factors that decrease metabolism:
 Cardiovascular dysfunction
 Kidney failure
 Liver failure
 Genetics
 Starvation
Factors that increase metabolism:
 Certain drugs (dilantin, barbiturates, rifampin)
Delayed drug metabolism results in:
 Accumulation
 Prolonged
of drugs (toxicity)
action of the effects of drugs
 Elimination
of drugs from the body
 All drugs must eventually be excreted
 Kidney = organ most responsible for
excretion of drugs (urine)
 Also, liver (bile), bowel (feces), sweat glands
 Liver metabolizes most drugs, kidney
excretes what is “left behind”
 Kidneys can also metabolize certain drugs

insulin
 Time
required to eliminate (½) 50% of a drug
 Example:
Digoxin - 36 hr. half-life
 Takes 7.5 (up to 9) days to clear

 Takes
5–6 half-lives to eliminate ~ 98% of a
drug
 Liver or kidney disease
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Can prolong half-life
Increases risk of toxicity
# of half lives
remainder of drug
1
50 %
2
25 %
3
12.5 %
4
6.25 %
5
3.125 %
Onset
 The time it takes for the drug to elicit a
therapeutic response
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Insulin: 10-20 min
Peak
 The time it takes for a drug to reach its
maximum therapeutic response
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30-60 min
Duration
 The time a drug concentration is sufficient to
elicit a therapeutic response
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2-4 hours
 Peak
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Peak effect, maximum therapeutic response
Highest blood level of the drug
If too high = toxicity of drug
 Trough
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Lowest blood level of the drug
If too low, then may not be therapeutic
 Furosemide
(LASIX)
 Pharmaceutics: Tablet, Oral solution, Injection
 Pharmacokinetics:
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Absorption: Bioavailability = 64% tablet, 60% oral soln,
100% IV
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Tablet, oral soln – 60 min. delay if taken w/ food
Distribution: highly protein bound to albumin, 91-99%
Metabolism: metabolized in liver
Elimination: excreted by kidneys
Onset:
1 hr. (oral)
5 minutes (IV)
*store
Peak:
1-2 hr. (oral) ½ hr. (IV)
room
Duration: 6-8 hrs. (oral) 2 hrs. (IV)
temp
 Mechanism
of drug action - how drugs act at
sites of activity
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Involves receptors and enzymes
Not all drugs have a known mechanism of action
Most drugs produce more than one effect
 Therapeutic effect – desired or primary effect
 Secondary effect – may be desirable or not

1. Drug-receptor interaction: drug binds to a receptor
site on cell surface, causes or blocks an action
2. Enzyme interaction: drug binds to enzyme molecule &
either enhances or inhibits its action
3. Nonselective interactions: do not bind to enzyme or
receptor, act on cell membrane or cell wall
 Drug-Receptor
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Drug binds to specific receptor
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Alters cell function
Produces desired effect
Can bind completely or partially
Agonists
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Interaction
Drugs that bind and produce desired effect
 example, Morphine
Antagonist
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Drugs that block agonist effect at binding site
 example, Narcan, reverses effect of narcotic
 Example, Toprol, beta-blocker, lowers HR
 Enzyme
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Interaction
Drug interacts with enzyme system
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Inhibits the action of the enzyme
The action of the cell is changed or altered
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
Example: ACE inhibitor (Lisinopril)
Inhibits conversion of angiotensin I to angiotensin II
 The
treatment of pathologic conditions
through the use of drugs
“drug therapy”
 Desired
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therapeutic outcome
Should be established before drug started
What is expected ?
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Must be measurable and realistic
Progress must be monitored (example = antibiotics)
 Types
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of therapy
Acute
Maintenance
Supplemental
Palliative
Supportive
Prophylactic
Empiric
 Acute
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Involves more intensive drug therapy
Used in the acutely or critically ill
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therapy
Example: to maintain heart rate or BP
Usually needed to maintain life
ie – dopamine (vasopressor to maintain BP)
 Maintenance
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May not cure but prevents progression of disease
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therapy
May prevent progression
Used in chronic illnesses (example: hypertension,
diabetes)
ie – lisinopril, oral contraceptives
 Supplemental
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Replaces body substances needed to maintain
normal functioning
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May not be produced by the body
Produced in insufficient amounts
Example: Insulin
 Palliative
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therapy
therapy
Goal is to provide comfort
Used in end stage illnesses
Usually all other therapy has failed
Example: Morphine for pain
 Supportive
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
therapy
Maintains integrity of body functions while
patient recovering from illness
Examples

Providing fluids/electrolytes to prevent dehydration

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In vomiting or diarrhea
Blood products or blood volume expanders

Blood loss during surgery
 Prophylactic
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Used to prevent illness
Example: pre-op antibiotics, vaccines
 Empiric
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therapy
therapy
Use of a drug based on probability, certain
illness/disease has likelihood of occurrence
Example: Antibiotic for UTI before actual
diagnosis
 Adverse

effects – unintended effects
Side Effects
 Therapeutic
index – ratio of toxic level to
therapeutic level
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Low therapeutic index: difference between toxic
and therapeutic dose is low – dangerous !
Example: coumadin (anticoagulant)
 Tolerance
– Pts. decreasing response to
repeated doses

ie – valium, pain meds
 Dependence
for drug

addiction
– Physiologic or psychologic need
Patient’s condition - Physiological
 Age

Infants & children need ↓ dose
 Immature organ function

Elderly may require ↓ dose
 Decreased gastric acidity
 Dry mouth/decreased saliva
 Decreased liver blood flow/mass
 Increased body fat, decreased muscle mass
 Decreased kidney function
Patient’s condition - Physiological
 Weight
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Average = 150lb
Dosage adjustments

Large weight differences
 Gender
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Women
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Smaller
Different fat/water ratio
May need dosage adjustments
Patient’s condition - Pathological
 Liver/kidney
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
disease
Inability to metabolize/excrete one normal dose
before next drug given
Leads to drug toxicity
Lower doses are frequently given
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Liver disease
Kidney disease
 Allergic
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Reactions (hypersensitivity)
Usually begins after 2nd dose or more
May occur within minutes or delay for hours or
even days
Immune system views “drug” as foreign substance
Histamine is released
S/S = skin rashes, hives, itching (urticaria or
pruritis), facial swelling, difficulty breathing,
sudden LOC, throat swelling (angioedema),
wheezing
Anaphylactic Shock

Severe allergic rx, severe respiratory distress, life
threatening
Mr.
Carter has a rash and pruritis.
You suspect an allergic reaction and
immediately assess him for other
more serious symptoms. What
question would be most imortant to
ask Mr. Carter ?
A
78 y.o. man who has been diagnosed with a
URI tells the nurse that he is allergic to
Penicillin (PCN). Which is the most
appropriate response by the nurse ?




1. “that’s to be expected, lots of people are
allergic to penicillin”
2. “this allergy is not a big concern right now”
3. “what type of reaction did you have when you
took penicillin ?”
4. “drug allergies don’t usually occur in older
individuals”
 Idiosyncratic
reaction: unexpected reaction
in a particular patient, not common reaction
 Pharmacogenetics: study of genetic traits
that result in abnormal metabolism of drugs

ie: coumadin, codeine, psych drugs (chap. 5)
 Teratogenic
effects: result in structural
defects of in fetus
 FDA – 5 categories (A,B,C,D,X) of teratogens


Category A – studies show NO risk (multivitamin)
Category X – Completely contraindicated in
pregnancy, HIGH fetal risk
Category A
No risk to fetus in first, second or third trimesters
Category B
Studies have not shown fetal risk in animals, but no controlled
studies in pregnant women
Considered safe in all trimesters (benadryl,tylenol,PCN)
Category C
Animal studies have revealed adverse effects on fetus
Drugs should be given only if benefit outweighs risk
Category D
Positive evidence of harm to fetus
Use may be acceptable absolutely necessary (life threatening
situations)
Category X
Studies have shown fetal abnormalities, drug is completely
contraindicated (acutane, coumadin)
 The
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
study of natural drug sources
Plants
Animals
 Four
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Plants
Animals
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
main sources of drugs
Source of many hormone drugs (premarin – urine of
pregnant mares; insulin – pigs & humans; heparin –
pigs)
Minerals (salicylic acid, sodium chloride)
Laboratory synthesis
 Place
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drugs in similar categories
Similar general use
Similar mechanisms of actions
Similar contraindications
Similar precautions
Similar nursing implications
 Examples:
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Antibiotics
Antihypertensives
Antiepileptics
Sedatives
Anesthetics
Decongestants
Antineoplastics
Etc.
 Physicians
Desk Reference (PDR)
 U.S. Pharmacopia
 National Formulary
 Various Nursing Drug Handbooks/References

Davis Drug Guide