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Pharmacologic Principles Chapter 2 Cristen Walker, MS, CRNP Level I.

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Presentation on theme: "Pharmacologic Principles Chapter 2 Cristen Walker, MS, CRNP Level I."— Presentation transcript:

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 1 st (before absorbed) Oral Preparations Liquids, elixirs, syrupsFastest Suspension solutions Powders Capsules Tablets Enteric coated tablets Extended release tabletsSlowest *Extended Release (forms) = SR (slow release), CR (controlled release), XL (extended length)

11 Pharmaceutics Drug Dissolution & Absorption Parenteral Preparations » Do NOT have to dissolve 1 st » 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


19 Pharmacokinetics Absorption Routes that bypass the liver : – SublingualTransdermal – BuccalVaginal – Rectal*Intramuscular – IntravenousSubcutaneous – 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 5–6 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: min Peak The time it takes for a drug to reach its maximum therapeutic response 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, % – 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


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 2 nd 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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