Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. Some material was previously published. Slide 0 Pharmacology: Principles.
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Chapter 2 critical thinking case ofChapter 2 critical thinking case ofBasics of PharmacologyBasics of Pharmacology
Yvette, a new patient, has been diagnosed Yvette, a new patient, has been diagnosed by the physician as hypertensive. The by the physician as hypertensive. The
physician has prescribed two new physician has prescribed two new medications for her to take. Yvette is also medications for her to take. Yvette is also
taking several other medications for taking several other medications for osteoarthritis and allergies; these were osteoarthritis and allergies; these were
prescribed by another physician, but she prescribed by another physician, but she cannot remember all of the names. What cannot remember all of the names. What can you do to make certain you have all can you do to make certain you have all the right information about Yvette’s new the right information about Yvette’s new medications so that they will not cause medications so that they will not cause
any adverse or toxic reactions?any adverse or toxic reactions?
Providing definitions of the key words using the Providing definitions of the key words using the appendix or a medical dictionary.appendix or a medical dictionary.
Stating healthcare workers’ responsibilities in Stating healthcare workers’ responsibilities in regard to adverse reactions, side effects, and regard to adverse reactions, side effects, and toxic reactions.toxic reactions.
Defining a drug and an ideal drug.Defining a drug and an ideal drug. Describing the five fundamental categories of Describing the five fundamental categories of
pharmacology and how these factors influence pharmacology and how these factors influence medications in the body.medications in the body.
Describing the indications of medicationsDescribing the indications of medications
What is a Drug? What is an Ideal What is a Drug? What is an Ideal Drug? (cont’d.)Drug? (cont’d.)
Ideal drug:Ideal drug: produces no side effects or adverse reactionsproduces no side effects or adverse reactions produces same effect each time the same produces same effect each time the same
dose is givendose is given easy to administereasy to administer inexpensiveinexpensive easy to pronounce, remembereasy to pronounce, remember
What is a Drug? What is an Ideal What is a Drug? What is an Ideal Drug? (cont’d.)Drug? (cont’d.)
No drug is completely safe.No drug is completely safe. All drugs cause some side effects or adverse All drugs cause some side effects or adverse
reactions.reactions. Drug must be as safe as possible.Drug must be as safe as possible.
Should have no harmful effects when taken in high Should have no harmful effects when taken in high doses over a long period of time.doses over a long period of time.
Be aware of a drug’s effects in order to safely Be aware of a drug’s effects in order to safely administer medications.administer medications.
Pharmacognosy—The Origins of Pharmacognosy—The Origins of DrugsDrugs
Historically, drugs came from four basic Historically, drugs came from four basic sources:sources: plantsplants animalsanimals mineralsminerals synthetic substancessynthetic substances
Recently, recombinant DNA technology Recently, recombinant DNA technology (gene-splicing) is being used to create drugs.(gene-splicing) is being used to create drugs.
Pharmacokinetics—How the Body Pharmacokinetics—How the Body Processes DrugsProcesses Drugs
Involves four processes:Involves four processes: AbsorptionAbsorption: movement of a drug from its : movement of a drug from its
administration site into the bloodadministration site into the blood DistributionDistribution: movement of a drug from the : movement of a drug from the
blood into tissues and cellsblood into tissues and cells MetabolismMetabolism: physical and chemical alteration : physical and chemical alteration
of a drug in the bodyof a drug in the body ExcretionExcretion: removal of waste products from : removal of waste products from
Physical properties that affect absorption rates:Physical properties that affect absorption rates: solubilitysolubility pHpH absence or presence of food in stomachabsence or presence of food in stomach fat solubilityfat solubility length of contactlength of contact inhalation factors inhalation factors drug concentrationdrug concentration
Factors affecting drug distribution:Factors affecting drug distribution: permeability of capillaries to drug’s moleculespermeability of capillaries to drug’s molecules chemical makeup of drugchemical makeup of drug amount givenamount given size of personsize of person amount of protein in bloodamount of protein in blood drug’s ability to pass through tissue’s cell drug’s ability to pass through tissue’s cell
Barriers to drug distribution:Barriers to drug distribution: Blood-brain barrier (water-soluble electrolytes Blood-brain barrier (water-soluble electrolytes
cannot cross, but fat-soluble substances can)cannot cross, but fat-soluble substances can) Placental barrier (allows water and fat-soluble Placental barrier (allows water and fat-soluble
substances to cross)substances to cross) Selective distribution (drugs are attracted to Selective distribution (drugs are attracted to
Metabolism, or Biotransformation Metabolism, or Biotransformation (cont’d.)(cont’d.)
Factors affecting drug metabolism:Factors affecting drug metabolism: condition of livercondition of liver first-pass effect—rapid inactivation of some first-pass effect—rapid inactivation of some
oral medications by the liveroral medications by the liver age of patientage of patient drug half-life—time in which half the available drug half-life—time in which half the available
drug is metabolized by the body for excretiondrug is metabolized by the body for excretion
Excretion or Elimination (cont’d.)Excretion or Elimination (cont’d.)
Factors affecting rate of excretion:Factors affecting rate of excretion: chemical composition of drugchemical composition of drug rate of metabolismrate of metabolism administration routeadministration route condition of excreting organscondition of excreting organs
good renal function essential good renal function essential milk glands also excrete some medicationsmilk glands also excrete some medications
Nursing mothers should check with physician Nursing mothers should check with physician before taking any medication.before taking any medication.
Pharmacodynamics—Action of Pharmacodynamics—Action of Drugs in the BodyDrugs in the Body
Drug actionDrug action: physiological change occurring : physiological change occurring in the body in response to the drug.in the body in response to the drug.
Drugs cannot give body organs and tissues Drugs cannot give body organs and tissues new functions.new functions.
Drugs can slow down or speed up cell Drugs can slow down or speed up cell processes.processes.
Drugs can replace natural substances, Drugs can replace natural substances, protect body from foreign materials, and protect body from foreign materials, and inhibit cell growth.inhibit cell growth.
Pharmacodynamics—Action of Pharmacodynamics—Action of Drugs in the Body (cont’d.)Drugs in the Body (cont’d.)
Four major effects:Four major effects: depressiondepression: lessens body activity: lessens body activity stimulationstimulation: increases body activity: increases body activity irritationirritation: produces areas of inflammation: produces areas of inflammation demulcencedemulcence: produces soothing effect: produces soothing effect
Toxicology—Poisonous Effects of Toxicology—Poisonous Effects of DrugsDrugs
All drugs taken in excess act as poisons.All drugs taken in excess act as poisons. Medication dose can mean the difference Medication dose can mean the difference
between therapeutic effect and toxic effect.between therapeutic effect and toxic effect. Antidotes can be given to reverse overdose Antidotes can be given to reverse overdose
symptoms or stop toxic effects.symptoms or stop toxic effects.
Anaphylaxis:Anaphylaxis: severe, potentially fatal, allergic responsesevere, potentially fatal, allergic response occurs a short time after the drug is occurs a short time after the drug is
effectseffects Did the patient follow instructions Did the patient follow instructions
accuratelyaccurately When did the symptoms first When did the symptoms first
occur? How long after the first use occur? How long after the first use of the drug?of the drug?
Has the patient started anything Has the patient started anything else new or changed something? else new or changed something? Has a new household product been Has a new household product been used?used?
If the drug was discontinued, did If the drug was discontinued, did the signs and symptoms the signs and symptoms disappear?disappear?
Undesirable Effects (cont’d.)Undesirable Effects (cont’d.) If the drug was restarted did the same effects If the drug was restarted did the same effects
occur?occur? Could the illness cause the symptoms? Are the Could the illness cause the symptoms? Are the
signs and symptoms consistent with the signs and symptoms consistent with the diagnosis?diagnosis?
Could other drug or products that are being used Could other drug or products that are being used concurrently cause the reaction?concurrently cause the reaction?
Is there a possibility of a drug-drug or drug-food Is there a possibility of a drug-drug or drug-food interaction?interaction?
Allied health professional important in Allied health professional important in evaluating undesirable effectsevaluating undesirable effects
Patient education should include early Patient education should include early identification of possible unwanted reactionsidentification of possible unwanted reactions
Evaluate medications on an individualized Evaluate medications on an individualized basisbasis
Drugs attach to appropriate receptor sitesDrugs attach to appropriate receptor sites Drug molecules travel in the blood until they Drug molecules travel in the blood until they
reach and attach to receptor sitereach and attach to receptor site The better the fit of the drug to the receptor The better the fit of the drug to the receptor
site, the better is the expected responsesite, the better is the expected response Drugs may be used to prevent other Drugs may be used to prevent other
chemicals from attaching to a receptor sitechemicals from attaching to a receptor site
Agonists vs Antagonists vs Agonists vs Antagonists vs SynergismSynergism
Agonist – drug that mimics body functionAgonist – drug that mimics body function May compete with previously bound drugsMay compete with previously bound drugs
Synergist – One drug potentiates another Synergist – One drug potentiates another drugdrug
Antagonist – drug that binds to a receptor Antagonist – drug that binds to a receptor site and does not activate the sitesite and does not activate the site Prevents the activation of the receptor site by the Prevents the activation of the receptor site by the
agonist agonist Counteract the expected effects of other drugsCounteract the expected effects of other drugs
Potentiation – One drug prolongs or augments Potentiation – One drug prolongs or augments the effects of anotherthe effects of another
Tolerance – Long-term use of drug lessens the Tolerance – Long-term use of drug lessens the expected effectexpected effect
Summation – Two drugs are given together and Summation – Two drugs are given together and each drug has the expected effecteach drug has the expected effect
Cumulation (accumulation) – Drug is not Cumulation (accumulation) – Drug is not excreted as expected and it accumulates in the excreted as expected and it accumulates in the bodybody See Table 2-8See Table 2-8
Foods may react with drugs to induce toxic Foods may react with drugs to induce toxic effects or cause failure of therapyeffects or cause failure of therapy
Absorption may be decreased by food in the Absorption may be decreased by food in the stomachstomach
Some medications must be taken with food to Some medications must be taken with food to prevent gastric irritationprevent gastric irritation See Box 2-4 See Box 2-4
Yvette, a new patient, has been diagnosed by the Yvette, a new patient, has been diagnosed by the physician as hypertensive. The physician has physician as hypertensive. The physician has prescribed two new medications for her to take. prescribed two new medications for her to take. Yvette is also taking several other medications Yvette is also taking several other medications for osteoarthritis and allergies; these were for osteoarthritis and allergies; these were prescribed by another physician, but she cannot prescribed by another physician, but she cannot remember all of the names. What can you do to remember all of the names. What can you do to make certain you have all the right information make certain you have all the right information about Yvette’s new medications so that they will about Yvette’s new medications so that they will not cause any adverse or toxic reactions?not cause any adverse or toxic reactions?