15460884 Introduction to Pharmacology

7/30/2019 15460884 Introduction to Pharmacology

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INTRODUCTION TO PHARMACOLOGY HISTORY Early drug plants, animals & minerals 2700 BB earliest recorded drug use founn Middle East & China 1550 BC Egyptians created Ebers Medical Papyrus Castor oil laxative Opium pain Moldy bread wounds & bruises Galen (131-201 AD) Roman phcian; initiated common use of prescriptions 1240 AD introduction of apothecary system (Arab doctors) 1st set of drug standards & measurements (grains, drams, minims), currently being phased out 15th century apothecary shops owned by barber,surgeons, physicians, independent merchants 18th century small pox vaccine (byJenner) Digitalis from foxglove plant for strengthening & slowing of heartbeat Vitamin C from fruits 19th century morphine & codeine extract from opium Introduction of atropine & iodine Amyl nitrite used to relieve anginal pain Discovery ofanesthetics (ether, nitrous oxide) Early 20th century aspirin from salicylic acid Introduction of Phenobarbital, insulin, sulforamides Mid 20th century 1940 Discovery antibiotics (penicilline, tetracycline, streptomycin), antihistamines, cortisone

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1950 discovery antipsychotic drug, antihypertensives, oral contraceptives, poliovaccine

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DEFINITION & SUBDIVISIONSDrug chemical introduced into the body to cause some changes WHO def: any product/subs used to modify/explore physiologic system/pathologic states for the benefit of the patient Pharmacology study of the manner in which the function of living system is affected by chemical agents/drugs Science concerned with history, sources, physical & chemical properties of drugs & the way in which drug affectsliving system

Subdivisions of pharmacology:1. pharmacodynamics study of the biochemical & physiological effects of drugs &mechanisms of action what the drug does to the body

2. pharmacokinetics deals with the absorption, distribution, biotransformation &excretion of drugs what the body does to the drug

3. pharmacotherapeutics study of drugs used in the diagnosis, prevention, suppression, & treatment of diseases deals with beneficial effects of the drugs (medicines)

4. pharmacognosy study of drugs in their original unaltered state; origin of drugs source of drugs ex: penicillin from penicillium (fungi)

5. Toxicology study of biologic toxins: study of poison & its effects deals withdeleterious effects of physical & chemical agents (including drugs) in human Pharmacoeconomics study of relationship of drugs & economics


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Pharmacovigilance science of collecting,researching, analyzing, & evaluating setof information about adverse drug effects. Receptor a component of the cell that interacts with drug, initiating a chain of biochemical events leading to drugsobserved effects Human body works through complicated series of chemical reactions & processes Important aspects of nursing: understanding how drug ant on bodyto cause changes & apply that knowledge in clinical setting Patients take complicated drug regimen & receive potentially toxic drug Some manage their own care at home Nursing responsibilities regarding drug therapy: Administering drugs Assessing drug effects Intervening to make drug regimen more tolerable Provide patient teachings about drugs & drug regimen Knowing how drug works --- easier to handle --- enhances drug therapy

DRUG NOMENCLATURE1. CHEMICAL NAME atomic/molecular structure of drug 2. GENERIC NAME/NON-PROPERTYNAME original designation given to the drug when the drug company applies for approval patents universally accepted & not capitalized; before drug becomes official, used in all countries protected by law; not capitalized 3. TRADE/BRAND/PROPRIETY NAME name given by the drug company that developed it followed by the symbol R or TM, 1st letter is capitalized chemical name acetylsalicylic acid generic name aspirin trade name aspilet


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COMMON SOURCES /4 MAJOR SOURCES (ORIGINS) OF DRUGS:1. Animal sources from organs, organ secretion or organ cells Used to replace human chemical not produces because of disease or genetic problems Thyroid drugs &growth hormones preparations from animal thyroid & hypothalamus tissue (many ofthese preparations are now created synthetically safer & purer) Insulin from pancreas of animals (hog, cattle, sheep): thru genetic engineering cld produce human insulin by altering E. coli bacteria making it a better product without impurities that come with animal products 2. vegetable/plant sources roots, bark, sap, leaves, flowers, seeds of medicinal plants digitalis from wildflower, purple foxglove, dried leaves of plant active principles of plants alkaloids alkaline inreaction, bitter in taste, powerful in physiologic activity o atropine & scopolamine o morphine sulfate, cocaine, quinine, nicotine, caffeine o procaine glycoides digitalis resin soluble in alcohol; example colonic irritant found in laxative cascara gums used in bulk-type laxatives: some used in certain skin preparations for their soothing relief oils castor oil, oil of wintergreen

3. Mineral sources from free elements, both metallic & non-metallic usually in form of acids bases, salts found in food


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Dilute HCI control/prevent indigestion Calcium, aluminum, fluoride, iron, gold,potassium

4. synthetic sources many drugs developed synthetically after chemical in plants, animals, or environment have been screened for signs of therapeutic activity ore potent, more stable, less toxic steroids arthritis & other diseases sulfonamides/chemotherapeutic agents kill microorganism slow their growth meperidine HCI(Demerol)

DRUG CLASSIFICATIONA. by action Anti infectives antiseptics, disinfectants, sterilantsls, metabolic, diagnostic materials, vitamins & minerals Vaccine & serums, antifungals, antihistamines, antineoplastics, antacids

B. By body system CNS (+)/(-) actions of neural pathways & centers: Phenobarbital ANS governs several bodily functions so that drugs that affect ANS will at thesame time affect other systems functions GIT acts on mascular & glandular tissues: leperamide RESPIRATORY SYSTEM act on resp. tract, tissues, cough center, suppress, relax, liquefy & stimulate depth & rate of respiration Urinary system acton kidney & urinary tract Circulatory system act on heart, blood vessels, blood; metoprolol

KINDS OF DRUGSPrescription/legend drug can be dispensed if with prescription order; with specific name of drug & dosage regimen to be used by patient


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non-prescription drug can be dispensed over the-counter/without prescription order for self treatment of variety of complaints vitamin supplements, cold/cough remedies, analgesics, antacids, herbal products cautions in use of OTC drugs: 1. delay in professional diagnosis & treatment of serious/potentially serious condition may occur 2. symptoms may be masked making the diagnosis more complicated 3.clients health care provider/pharmacist should be consulted before OTC preparations are taken 4. labels/instructions should be followed carefully 5. ingredientsin OTC drug may interact with prescribed drug 6. inactive ingredients may result in adverse reactions 7. potential for overdose 8. multiple medication users are at risk as more medications are added to therapy regimen 9. interactions of medications are potentially dangerous Investigational drug new drugs undergoing clinical trails Illicit/street drug used/distributed illegally for non-medical purposes to alter mood of feeling **when drug is taken by mouth, it undergoes 3 phases: 1. pharmaceutic/dissolution 2. pharmacokinetics 3. pharmacodynamics

I. PHARMACEUTIC/DISSOLUTIONDrug goes into solution so that it can cross the biologic membrane Not found indrug administered parenterally 1st phase of drug action of agents taken by mouth


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Additive enhances absorbability of drugs EXCIPIENTS: filters & inert substances

Allows drugs to take on particular size & shape Enhance drug dissolution potassium (K) --- losartan K (cozaar); sodium (Na) ---cloxacillin Na (Prostaphlin-A) 2phases: Disintegration breakdown into smaller parts Dissolution futher breakdowninto smaller parts in GIT absorption; dissolved into liquid rate limiting: timeit takes drug to disintegrate & dissolve to become available for body to absorbit factors affecting dissolution form of drug (LIQUID VS. SOLID) liquid more absorbed than solid, already in solution, rapidly available for GI absorption Gastric ph (acid vs alkaline) acidic media (ph=1.2) faster disintegration & absorption Age young vs elderly inc ph. Dec absoption Enteric coated drugs resist disegration in gastric acid Disintegration occurs only in alkaline environment (intestine) Should not be crushed Presence of food interfere with dissolution & absorption, enhance absorption of other drugs, may be protectants of gastric mucosa

I. PHARMACOKINETICS action of body to the drug: Study of absoption (taken into the body), distribution (moved into various tissues), metabolism/biotransformation (changed into a form that can be excreted) & excretion (removed from the body)of drugs What happens to the drug when it enters the body kinetics movement: deas with drugs actions as it moved through the body


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Also concerned with a drugs onset of action, peak concentration level, & durationof action

4 processes involved: I. Absorption route of drug takes from the time it entersthe body until it is absorbed in circulating fluids Movement of drug molecules from site of administration to circulatory system Movement of drug particles fromGIT to body fluids involve 3 processes Passive absorption (diffusion) movementfrom higher concentration o No energy required: occurs when smaller molecules diffuse across membrane o Stops when drug concentration on both sides of the membrane is equal o Major process through which drugs are absorbed into the body Active absorption needs carrier (enzymes or protein) to move against a concentrationgradient o Energy is required: from lower concentration to higher concentrationo Used to absorb electrolytes (i.e. sodium, potassium) & some drugs (levodopa) Pinocytosis engulfs the drug to carry it across the membrane o Transport fat-soluble vitamins (vit.A,D,E,K) Factors affecting absorption: Drug solubility lipidsoluble drugs pass readily through GI membrane, Water soluble drugs need an enzyme or protein


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Local condition at site of absorption weak acids less ionized in stomach

- - - readily pass through the SI Pain / stress / solid foods / fatty or hot foods slows down gastric emptying time Drug concentration drugs can take several hours/days to reach peak concentration levels (slow rate: rectal administration orsustained release drugs) Circulation at site of absorption poor circulation hampers absorption (i.e. shock) The more blood vessels, the faster the absorption Exercise decrease blood flow to GI slows absorption Application of heat/massage increases blood flows at site Muscles area selected for IM administration: Bloodflows faster through deltoid muscle (upper arm) vs gluteal muscle (buttocks) Gluteal muscle can accommodate larger volume of drug than deltoid muscle 3. Metabolism biotransformation: essential for termination of a drugs biologic activity socan be easily excreted Sites of metabolism o Liver main organ for drug metabolism Through the drug metabolizing enzymes (microsomal enzymes, non-microsomal enzymes) 1st pass effect hepatic 1st pass some drugs do not directly go into circulation but pass thru intestinal lumen to liver via portal vein - - drug metabolized in liver into inactive form - - decrease


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amount of active drugs - - - increase recommended dose for oral drugs o Plasma oKidneys o Membranes of intestine Process by which body changes a drug from itsdosage form to a more watersoluble form that can then be excreted Can be metabolized in several ways: o Most drugs metabolized into inactive metabolites (products of metabolism), which are then excreted o Other drugs converted to active metabolites capable of exerting their own pharmacologic action May undergo furthermetabolism or may be excreted from body unchanged Prodrugs some drugs administered as inactive drugs which dont become active until theyre metabolized o Permits the body to inactive a potent drug before it accumulates & produces toxic effects Phases of drug metabolism: o Phase 1: endoplasmic reticulum; introduce/expose afunctional group on the parent compound (i.e. alkylation, alipathic hydroxylation, oxidation, deamination, hydrolysis, microsomal oxidases) Cytochrome p450 inducer inc drug metabolism, dec bioavailability Cytochrome p450 inhibitor dec drugmetabolism, inc levels of drug prolonged effect & inc toxicity o Phase 2 conjugation reactions that lead to formation of covalent linkage between parent compound with glucoronic acid, sulfate, Lidocaine extensive 1st pass not given orally


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glutathione or acetate (glucoronidation, sulfation, acetylation); synthetic reactions Factors affecting biotransformation: o Genetic some people metabolize drugs rapidly, other more slowly o Physiologic Liver diseases (cirrhosis), heart failure dec circulation in liver Infants immature livers dec rate of metabolism

o Area of absorbing surface to which a drug is exposed (+) chemical agents may destroy the drug o Types of transport diffusion, active, pinocytosis o Routes ofadministration skin absorption slower than IM Absorption with in seconds/minutes: sublingual, IV, by inhalation route Slower rate absorption: oral, IM SC routeso Bioavailability consideration of highest importance in drug effectiveness & safety Subcategory of absorption % of administered drug does that reaches systemc circulation Oral route


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the ways a drug is transported from the site of administration to the site of action (transportation) factors affecting distribution: o size of the organ o blood flows drug is quickly distributed to organs with large supply of blood (heart,liver, kidneys) distribution to other internal organs, skin, fat, muscle is slower o solubility lipid soluble drugs can also cross the blood-brain barrier & enter the brain o Binding as drug travels trough the body, it comes in contract with proteins (albumin). The drug can remain free or bind to protein. Portion of drug bound to protein is inactive, no therapeutic affect Free/unbound portion active - - - - (+) pharmacologic response Highly protein bound drug - > 89% of drugis bound to protein Diazepam, piroxicam, valproic acid

Moderately highly protein bound drugs (61-89% bound protein) Erythromycin, phenytoin

Moderately protein bound drugs 30-60% Aspirin, lidocaine, pindolol, theophyliine

Low protein-bound drugs - < 30% bound to protein (amikacin, amoxicillin)

DISTRIBUTION

PROTEINBINDING

BLOOD FLOW

BODY TISSUE AFFINITY

PHARMACOLOGIC EFFECT


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Elderlies dec liver size, blppd flow, enzyme production - - - slows metabolism Environment cigarette smoke may affect rate of some drugs o Stressful environment prolonged illness, surgery, injury

III. Excretion/elimination removal of drug from the body: drug is changed into inactive form & excreted by the body Routes: o Kidney main organ for drug elimination: leaves the body through urine tract Factors affecting drug excretion o Urne ph normal: 4-5.8 Acid urine promotes elimination of weak base drugs i.e. craberry juice dec urine ph - - - (-) elimination of aspirin alkaline urine (+) elimination of weak acid drug overdose aspirin - - - give Nabicarbonate inc urine ph - - - (+) excretion of drug Free/unbound/water soluble drugs filtered in kidney Protein bound drug cannot be filtered in kidney (+) kidney dose dose must be decreased

o Lungs, exocrine (sweat, salivary, mammary) glands, skin, intestinal


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o glomerular filtration rate (GFR) dec GFR - - - drug excretion slowed/impaired can result to drug accumulation extent of filtration directly proportional to GFR & to fraction of unbound drug to plasma ratio of clearance = fu x GFR - - - cleared by filtration ratio of clearance < fu x GFR - - - cleared tubular reabsorption ratio of clearance > fu x GFR - - - cleared by tubular secretion o creatinine clearance most accurate test to determine renal function creatinine excretedin kidney dec renal GFR inc serum creatinine level & dec urine creatinine clearance 12-24 hrs urine collection & blood sample Normal 85-135 ml/min; elderly 6/min

Renal clearance amount of substance removed from the blood by the kidneys Half-life/elimination half-life (t ) time it takes for one half of drug concentration to be eliminated o Short t = 4-8 hrs: given several times a day (i.e. penicillinG) o Long t = > 12 hrs: given 2x or 1x / day (digoxin)

II. PHARMACODYNAMICS refers to action of drug to the body What happens to the body in response to the drug Effects of drugs on the cells biological & physiological functions & mechanisms of action Interactions between chemical components ofliving systems & foreign chemicals including drugs that enter these system


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Mechanism of action: means by which a drug produces alteration in function of their action Drug actions: a. To replace/act as substitute for missing chemicals b. To inc or stimulate certain cellular activities c. To depress/slow cellular activities d. To interfere with functioning of foreign cells (i.e. invading microorganisms/neoplasms) chemotherapeutic Agents Theories of Drug Actions a. Drug-receptors interaction certain portion of drug molecule (active site) selective combines with some molecular structure (reactive site) on the cell to produce a biologic effect Receptor site drugs act at specific areas on cedil memb.; react withcertain chemicals to cause an effect with in cell lock & key theory specific cheical (key) approaches a cell membrane & finds a perfect fit (the lock) at receptor site affects enzymes system within a cell produce certain effects Specificit selectivity theory Drug action may be: Agonists drugs that produce a response oinsulin reacts with specific insulin receptor site to change cell membrane permeability - - - (+) movement of glucose into cell competitive antagonist act withreceptor sites to block normal stimulation producing no effect o curare use onspear in Amazon to paralyze prey & cause death: occupies receptor sites for Acetylcholine (needed in muscle contraction & movement) - - - prevents nerve stimulation causing paralusis


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o noncompetitive antagonist - prevent reaction of another chemical with different receptor site on that cell b. drug-enzymes interaction interferes with enzymesystems that act as catalyst from various chemical reations enzyme systems cascade effect; one enzyme activating another - - - causing cellular reaction if single step in one of enzyme system is blocked normal cell function is disrupted ex:acetazolamide (diamox) diuretic that block carbonic anhydrase alters H+ & H2O exchange systems in kidneys & eye c. nonspecific drug interaction act by biophysical means that do not affect cellular enzymatic reactions d. selective toxicity all chemotherapeutic agent would act only on 1 enzyme system needed for life ofa pathogen or neoplastic cell & will nor affect healthy cells ex: penicillin unfortunately most of it cause destruction of normal human cells Drug response maybe: 1. primary always desirable / physiologic effects 2. secondary desirable orundesirable ex: diphenhydramine (benadryl) 1st effect: antihistamine, treat symptoms of allergy; 2: CNS depression - - - drowsiness desirable: when given at bedtime: undesirable: when client is driving Classification of drug action: 1. rapid few seconds to minutes (IV, SL, inhalation) 2. intermediate 1-2 hrs after administration (IM, SC)


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3. Delayed/slow several hrs after administration (rectal, oral) Parameters of Drug Action: 1. onset of action latent period: interval between time drug is administered & 1st sign of its effect time it takes to reach the minimum effective concentration (MEC) after a drug is administered time from drug administration to1st observable effect _T0 T1)

2. duration of action period from onset until drug effect is no longer seen length of time the drug exerts pharmacologic effect (T1 T3)

3. peak action drug reaches its highest blood / plasma concentration (T0 T2) Termination of action point from onset at which drug effect is no longer seen Minimal effective concentration lowest plasma concentration that produces the desireeffect Peak plasma level highest plasma concentration attained from a dose Toxiclevel plasma concentration at which a drug produces adverse effects Therapeuticrange range of plasma concentration that produces the desire effect without toxicity (range between minimal effective concentration & toxic level) Loading dose bolus of drug given initially to attain rapidly a therapeutic plasma concentration large initial dose; when immediate drug response is desired given to achievea rapid MEC in the plasma i.e. digoxin - - - requires LD

Maintenance dose amount of drug necessary to maintain a steady therapeutic plasma concentration Dose response relationship between minimal vs. maximal amount ofdrug dosed needed to produce desired drug response i.e. some clients respond tolower drug dose while others need a high dose


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Maximal efficacy (maximum drug effect) all drugs give a maximum drug effect (maximal efficacy) i.e. simvastatin 40mg vs rouvastatin 10mg

Drug-response relationship: Biologic half-life (t1/2) = time required to reduceto amount of unchanged drug that is in the body short t1/2 drugs need to be administered more often than one with a longer t1/2 Lethal dose (LD50) dose lethal to 50% of animals tested Effective dose (ED50) dose required to produce therapeutic effect on 50% animals tested Therapeutic index (TI) ratio between LD50 and ED50; the closer the ratio is to 1, the greater the danger involved in giving thedrug to humans estimates the margin of safety of a drug through the use of a ratio that measures the effective (therapeutic or concentration) dose (ED) in 50% of persons/animals (ED50) & lethal dose in 50% of animals (LD50) TI=LD50/ED50 lowtherapeutic index: narrow margin of safety; might need to adjust drug dose & plasma drug levels need to be monitored high therapeutic index: wide margin of safety less danger of producing toxic effects 4 Categories of Drug Action: 1. stimulation/depression stimulation inc rate of cell activity/secretion from the glanddepression dec cell activity & function of a specific organ

2. replacement replaces essential body compounds; i.e. insulin 3. inhibition/killing of organism interfere with bacterial cell growth ; i.e. antibiotics


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4. irritation i.e. laxative irritate inner wall of colon - - - inc peristalsis -- - inc defecation Drug potency relative amount of drug required to produce desired response also used to compare a drug

dose response curve graphical representation of relationship between dose of drug & response it produces low dose low response dosage increased produce slight increase response, as dose further increases, drug response increases markedly, at certain point however, inc dose yield little or no inc in response - - - drughave reached Maximum Effectiveness Factors Affecting Dose Response Curve: nursemust be aware that human factor has tremendous influence on what actually happens when it enter the body no 2 people react in exactly the same way to any givendrug 1. weight heavier patient larger dose to get therapeutic effect (more tissue to perfuse & inc receptor site in some reactive tissues) 3. toxicity 4. pharmacogenetics effect of a drug action that varies from a predicted drug response because of genetic factors or hereditary influence people have different genetic makeup do not always respond identically to a drug dosage or planned drug therapyex: African Americans do not respond as well as whites to some classes of antihypertensive medications 5. route of administration dec weight dec dose older patients: less absorption, distribution between fewer plasma proteins & less efficient perfusion: geriatric dosages nurse should monitor closely for desired effects (may adjust dose) 2. age children (immune system for handling drugs) & older adults


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6. emotional factors 7. pre-existing disease state liver disease 8. drug history drug interaction synergistic/excretion 9. tolerance 10. cumulative effect 11. drug- drug interaction 12. BMR inc BMR inc drug metabolism & excretion Drug Interaction 1. Additive effect 2 drugs with similar actions are taken for a doubled effect (desirable/undesirable) (1 + 1 = 2) Ibuprofen + paracetamol + added analgesic effect

2. Synergistic combined effect of 2 drugs is greater than sum of the effect or each drug given alone (1 + 1 = 3) Aspirin + codeine = greater analgesic effect

3. potentiation a drug that has no effect enhances the effect of a 2nd drug (0 +1= 2) 4. Antagonistic one drug inhibits the effect of another drug (1 + 1 = 0) Tetracycline + antacid = dec absorption of tetracycline

SIDE EFFECTS Physiologic effects not related to desired drug effects All drugs have side effects Desirable: diphenhydramine (Benadryl) at bedtime s/e: drowsiness Undesirable

Result mostly from drugs that lack specificity Might be used interchangeably with adverse reactions Not a reason to discontinue drug therapy Nurses role: teach clients to report any side effects


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ADVERSE REACTIONS More severe than side effects Range of untoward effects (uninended, occurring at normal doses) of drug that cause mild-severe side effects: anaphylaxis (cardiovascular collapse) Always undesirable Must always be reported& documented because they represent variances from planned therapy. TOXIC EFFECT/TOXICITY Can be identified by monitoring the plasma (serum) therapeutic range of the drug Narrow TI (aminoglycoside & antibiotics) therapeutic range is monitored When drug level exceeds therapeutic range, toxic effects are likely to occurfrom overdosing or drug accumulation.


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15460884 Introduction to Pharmacology

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Transcript of 15460884 Introduction to Pharmacology