Introduction to Pharmacology NAPNES Guidelines
Download
Report
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:
Absorption
Distribution
Metabolism
Excretion
Mechanism of Action
Therapeutic effects
Adverse effects
Subspecialty
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
Design that will allow drug molecules to bind
to a target site
Drug
Oral
Intramuscular, Subcutaneous, Intravenous,
Topical
Via intestine
Via NG tube, feeding tube (or rectal)
Rectal
Parenteral
Via mouth
Includes sublingual, buccal
Enteral
routes
Directly applied to skin
Mucosal
**Forms/designs of drugs:
Oral
Tablets, capsules, powder, liquid, elixir, suspension
EC, ER, SR
Enteral
Meds given via NG or feeding tube (solid or liquid)
Crushed meds – must be dissolved
Rectal
Suppositories, creams, enema
Also considered as ENTERAL route
Parenteral
Injections (solutions, powder)
Topical
Ointments, creams, pastes, powders, patches
Mucosal
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
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
Extent of drug absorption
Amount of drug actually available to circulation
Depends upon “first pass effect”
Example: Aspirin
Has high “first pass effect”
First
Drugs must dissolve & be absorbed by GI tract
Must pass through LIVER before reaching
circulation (bloodstream)
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
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
Transport
of drug by bloodstream to site of
action
Areas of “rapid” distribution
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
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
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
Insulin: 10-20 min
Peak
The time it takes for a drug to reach its
maximum therapeutic response
30-60 min
Duration
The time a drug concentration is sufficient to
elicit a therapeutic response
2-4 hours
Peak
Peak effect, maximum therapeutic response
Highest blood level of the drug
If too high = toxicity of drug
Trough
Lowest blood level of the drug
If too low, then may not be therapeutic
Furosemide
(LASIX)
Pharmaceutics: Tablet, Oral solution, Injection
Pharmacokinetics:
Absorption: Bioavailability = 64% tablet, 60% oral soln,
100% IV
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
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
Drug binds to specific receptor
Alters cell function
Produces desired effect
Can bind completely or partially
Agonists
Interaction
Drugs that bind and produce desired effect
example, Morphine
Antagonist
Drugs that block agonist effect at binding site
example, Narcan, reverses effect of narcotic
Example, Toprol, beta-blocker, lowers HR
Enzyme
Interaction
Drug interacts with enzyme system
Inhibits the action of the enzyme
The action of the cell is changed or altered
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
therapeutic outcome
Should be established before drug started
What is expected ?
Must be measurable and realistic
Progress must be monitored (example = antibiotics)
Types
of therapy
Acute
Maintenance
Supplemental
Palliative
Supportive
Prophylactic
Empiric
Acute
Involves more intensive drug therapy
Used in the acutely or critically ill
therapy
Example: to maintain heart rate or BP
Usually needed to maintain life
ie – dopamine (vasopressor to maintain BP)
Maintenance
May not cure but prevents progression of disease
therapy
May prevent progression
Used in chronic illnesses (example: hypertension,
diabetes)
ie – lisinopril, oral contraceptives
Supplemental
Replaces body substances needed to maintain
normal functioning
May not be produced by the body
Produced in insufficient amounts
Example: Insulin
Palliative
therapy
therapy
Goal is to provide comfort
Used in end stage illnesses
Usually all other therapy has failed
Example: Morphine for pain
Supportive
therapy
Maintains integrity of body functions while
patient recovering from illness
Examples
Providing fluids/electrolytes to prevent dehydration
In vomiting or diarrhea
Blood products or blood volume expanders
Blood loss during surgery
Prophylactic
Used to prevent illness
Example: pre-op antibiotics, vaccines
Empiric
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
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
Average = 150lb
Dosage adjustments
Large weight differences
Gender
Women
Smaller
Different fat/water ratio
May need dosage adjustments
Patient’s condition - Pathological
Liver/kidney
disease
Inability to metabolize/excrete one normal dose
before next drug given
Leads to drug toxicity
Lower doses are frequently given
Liver disease
Kidney disease
Allergic
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
study of natural drug sources
Plants
Animals
Four
Plants
Animals
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
drugs in similar categories
Similar general use
Similar mechanisms of actions
Similar contraindications
Similar precautions
Similar nursing implications
Examples:
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