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Pharmacologic Principles Chapter 2

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Title: Introduction to Pharmacology NAPNES Guidelines Author: Laura Zdancewicz Last modified by: cwalker Created Date: 9/6/2004 12:57:33 PM Document presentation format – PowerPoint PPT presentation

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Title: Pharmacologic Principles Chapter 2


1
Pharmacologic
Principles Chapter 2
  • Cristen Walker, MS, CRNP
  • Level I

2
Pharmacology
  • 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
  • Toxic effects

3
Pharmacology
  • Subspecialty Areas of Pharmacology
  • Pharmaceutics
  • Pharmacokinetics
  • Pharmacodynamics
  • Pharmacotherapeutics
  • Pharmacognosy
  • Toxicology
  • NURSES MUST UNDERSTAND BASIC PRINCIPLES OF
    PHARMACOLOGY
  • Therapeutic and Toxic

4
Pharmacology Drug development
  • Drugs will acquire 3 names
  • CHEMICAL (N-4 hydroxyphenyl acetamide)
  • Drugs chemical composition, molecular structure
  • GENERIC (acetaminophen)
  • Shorter than chemical name
  • Used as official listing of drugs
  • TRADE (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

5
Pharmacology Drug Development
6
Pharmaceutics
  • Process of turning chemicals into safe
    medications
  • Science of dosage form design
  • ie tablet, capule, liquid, powder, etc.
  • Study of how various dosage forms/designs
    influence a drugs metabolism and use in the body

7
Pharmaceutics
  • Drug routes
  • Oral
  • Via mouth
  • Includes sublingual, buccal
  • Enteral
  • Via intestine
  • Via NG tube, feeding tube (or rectal)
  • Rectal
  • Parenteral
  • Intramuscular, Subcutaneous, Intravenous,
  • Topical
  • Directly applied to skin
  • Mucosal

8
Pharmaceutics
  • 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)

9
Pharmaceutics
  • Topical
  • Ointments, creams, pastes, powders, patches
  • Mucosal
  • eye, ear, nasal, vaginal
  • Inhaled

10
Pharmaceutics
  • Drug Dissolution Absorption
  • Drugs must dissolve 1st (before absorbed)
  • Oral Preparations
  • Liquids, elixirs, syrups FastestSuspension
    solutions êPowders êCapsules êTablets êEnteric
    coated tablets êExtended release
    tablets Slowest
  • Extended Release (forms) SR (slow release), CR
    (controlled release), XL (extended length)

11
Pharmaceutics
  • Drug Dissolution Absorption
  • Parenteral Preparations
  • Do NOT have to dissolve 1st
  • Subcutaneous, Intramuscular
  • Intravenous
  • directly into bloodstream
  • immediate absorption

12
Pharmacokinetics
  • Study of what happens to a drug from entrance
    into body until it leaves the body
  • 4 phases
  • Absorption
  • Distribution
  • Metabolism
  • Excretion

13
Pharmacokinetics - absorption
  • 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.)

14
PharmacokineticsAbsorption
  • Factors That Affect Absorption
  • Administration route
  • Dosage formulation
  • Food or fluids administered with the drug
  • Grapefruit, fruit juices, antacids, fat soluble
    vitamins
  • Rate of blood flow to the small intestine
  • Acidity of the stomach
  • Status of GI motility

15
Pharmacokinetics - Absorption
  • Bioavailability
  • Extent of drug absorption
  • Amount of drug actually available to circulation
  • Depends upon first pass effect

16
Pharmacokinetics - absorption
  • First Pass effect
  • Drugs must dissolve be absorbed by GI tract
  • Must pass through LIVER before reaching
    circulation (bloodstream)
  • Drug GI system Portal vein
    Liver
  • Hepatic vein Heart (distribution)
  • Liver may metabolize drug into smaller
    metabolites
  • Therefore, less amount of drug will pass into
    circulation
  • Intravenous drugs no first pass in liver

17
PharmacokineticsAbsorption
  • 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

18

19
Pharmacokinetics Absorption
  • Routes that bypass the liver
  • Sublingual Transdermal
  • Buccal Vaginal
  • Rectal Intramuscular
  • Intravenous Subcutaneous
  • Intranasal Inhalation
  • Rectal drugs may have some degree of first-pass
    effect

20
PharmacokineticsAbsorption
  • Parenteral Route
  • No first pass effect
  • Intravenous
  • Intramuscular
  • Subcutaneous
  • Intradermal
  • Intraarticular (physician)
  • Fastest delivery into the blood circulation

21
PharmacokineticsAbsorption
  • 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

22
Pharmacokinetics Distribution
  • Transport of drug by bloodstream to site of
    action
  • Areas of rapid distribution
  • Heart
  • Liver
  • Kidneys
  • Brain
  • Areas of slower distribution
  • Muscle
  • Skin
  • Fat
  • Areas difficult to reach
  • Bone
  • Blood brain barrier

23
Pharmacokinetics - distribution
  • BLOOD BRAIN BARRIER
  • Restricts passage of various chemicals between
    the bloodstream and the central nervous system
  • CNS brain, spinal cord
  • BBB
  • allows oxygen to pass
  • may restrict certain bacteria viruses
  • Not all meds can pass through

24
Pharmacokinetics - distribution
  • 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

25
Pharmacokinetics Metabolism
  • 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

26
Pharmacokinetics Metabolism
  • Factors that decrease metabolism
  • Cardiovascular dysfunction
  • Kidney failure
  • Liver failure
  • Genetics
  • Starvation
  • Factors that increase metabolism
  • Certain drugs (dilantin, barbiturates, rifampin)

27
Pharmacokinetics Metabolism
  • Delayed drug metabolism results in
  • Accumulation of drugs (toxicity)
  • Prolonged action of the effects of drugs

28
Pharmacokinetics Excretion
  • 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

29
Pharmacokinetics Half-Life
  • Time required to eliminate (½) 50 of a drug
  • Example
  • Digoxin - 36 hr. half-life
  • Takes 7.5 days to clear
  • Takes 56 half-lives to eliminate 98 of a drug
  • Liver or kidney disease
  • Can prolong half-life
  • Increases risk of toxicity

30
Pharmacokinetics OnsetPeakDuration
  • 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

31
PHARMACOKINETICS ONSET-PEAK-DURATION
  • 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

32
Onset-Peak-Duration
33
Pharmacokinetics Example
  • 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

34
Pharmacodynamics
  • 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

35
Pharmacodynamics
  • Drug-Receptor Interaction
  • Drug binds to specific receptor
  • Alters cell function
  • Produces desired effect
  • Can bind completely or partially
  • Agonists
  • 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

36
Pharmacodynamics
  • 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

37
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38
Pharmacotherapeutics
  • 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)

39
Pharmacotherapeutics
  • Types of therapy
  • Acute
  • Maintenance
  • Supplemental
  • Palliative
  • Supportive
  • Prophylactic
  • Empiric

40
Pharmacotherapeutics
  • Acute therapy
  • Involves more intensive drug therapy
  • Used in the acutely or critically ill
  • Example to maintain heart rate or BP
  • Usually needed to maintain life
  • ie dopamine (vasopressor to maintain BP)
  • Maintenance therapy
  • May not cure but prevents progression of disease
  • May prevent progression
  • Used in chronic illnesses (example hypertension,
    diabetes)
  • ie lisinopril, oral contraceptives

41
Pharmacotherapeutics
  • Supplemental therapy
  • Replaces body substances needed to maintain
    normal functioning
  • May not be produced by the body
  • Produced in insufficient amounts
  • Example Insulin
  • Palliative therapy
  • Goal is to provide comfort
  • Used in end stage illnesses
  • Usually all other therapy has failed
  • Example Morphine for pain

42
Pharmacotherapeutics
  • 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

43
Pharmacotherapeutics
  • Prophylactic therapy
  • Used to prevent illness
  • Example pre-op antibiotics, vaccines
  • Empiric therapy
  • Use of a drug based on probability, certain
    illness/disease has likelihood of occurrence
  • Example Antibiotic for UTI before actual
    diagnosis

44
Adverse Effects - Monitoring
  • 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 Physiologic or psychologic need for
    drug
  • addiction

45
Adverse Effects Monitoring
  • Patients 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

46
Adverse Effects Monitoring
  • Patients condition - Physiological
  • Weight
  • Average 150lb
  • Dosage adjustments
  • Large weight differences
  • Gender
  • Women
  • Smaller
  • Different fat/water ratio
  • May need dosage adjustments

47
Adverse Effects Monitoring
  • Patients 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

48
Adverse Effects
  • 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

49
  • 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 ?

50
Adverse Effects
  • 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

51
Teratogens
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)
52
Pharmacognosy
  • The study of natural drug sources
  • Plants
  • Animals
  • Four main sources of drugs
  • Plants
  • Animals
  • Source of many hormone drugs (premarin urine of
    pregnant mares insulin pigs humans heparin
    pigs)
  • Minerals (salicylic acid, sodium chloride)
  • Laboratory synthesis

53
Drug Classifications
  • Place drugs in similar categories
  • Similar general use
  • Similar mechanisms of actions
  • Similar contraindications
  • Similar precautions
  • Similar nursing implications

54
Drug Classifications
  • Examples
  • Antibiotics
  • Antihypertensives
  • Antiepileptics
  • Sedatives
  • Anesthetics
  • Decongestants
  • Antineoplastics
  • Etc.

55
Drug References
  • Physicians Desk Reference (PDR)
  • U.S. Pharmacopia
  • National Formulary
  • Various Nursing Drug Handbooks/References
  • Davis Drug Guide
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