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Pharmacologic Principles . Jan Bazner-Chandler RN, MSN, CNS, CPNP Chapter 2. Pharmacology. The study or science of drugs Knowledge of pharmacology allows nurse to understand how drugs affects humans. . Naming the drugs. Chemical name Generic name Trade name. Chemical name.

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Pharmacologic Principles

Jan Bazner-Chandler RN, MSN, CNS, CPNP

Chapter 2

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  • The study or science of drugs

  • Knowledge of pharmacology allows nurse to understand how drugs affects humans.

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Naming the drugs

  • Chemical name

  • Generic name

  • Trade name

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Chemical name

  • Chemical composition and molecular structure

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Generic Name

  • Shorter and simpler than the chemical name

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Trade Name

  • Drugs registered trade mark

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  • How dosage forms influence the way in which the body metabolizes a drug and the way the drug affects the body.

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Dosage Forms

  • Tablets

  • Capsules

  • Sustained release tablet

  • Injection – “shot”

  • Sublingual – under the tongue

  • Intravenous - IV or directly into the vein

  • Topical

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  • The mechanism by which specific drugs produce biochemical and physiologic changes in the body.

    • A given drug interacts with specific receptor sites: agonist drugs stimulate receptors, antagonist drugs inhibit receptors

    • Causes general interaction with cell metabolism

    • Cellular environment and function are altered to produce the desired response.

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  • Movement of drugs across body membranes to reach the target organ.

  • 4 ways drugs move throughout the body:

    • Absorption

    • Distribution

    • Metabolism

    • Excretion

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  • Process that occurs from the time the drug enters the body to the time it enters the bloodstream to be circulated.

  • Onset of drug action is largely determined by the rate of absorption.

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  • Think of how the drug gets into the circulatory system and the dosage needed to bring the blood levels up to therapeutic levels.

    • Dosage

    • Interval of administration

    • Route of administration

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Oral Drugs or PO Drugs

  • Dosage is determined by how much of the drug is required to be taken by mouth to given the desired affect.

  • Bioavailability – portion of the drug that reaches the systemic circulation.

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  • If a drug is metabolized by the liver before it reaches the systemic circulation, some of the active drug will be inactivated or diverted before it can reach the general circulation.

  • Most drugs administered by mouth have less than 100% bioavailability.

  • Drugs administered by the intravenous route have 100% bioavailability.

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Critical thinking question

  • What are the effects on bioavailability in:

    • The infant that has an immature liver.

    • The geriatric patient with a poor functioning liver

    • The client with liver disease.

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Where does absorption happen?

  • Very few drugs actually absorbed in the stomach (alcohol)

  • Small intestine

    • large surface area for absorption of nutrients and minerals

    • most drugs absorbed in small intestine

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Degree and Rate of Absorption

  • Depends on

    • Route

    • Age and physical condition of client

    • Lipid or water solubility of drug

    • Potential drug interactions with other drugs

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What else might influence oral drug absorption?

  • Food in stomach

  • Certain juices – grapefruit juice

  • Milk – binds with molecules of some drugs so that the drug is never absorbed

  • Orange juice – enhances absorption of iron taken orally

  • The coating on the tablet: chewable, enteric coated, slow release capsules

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Local Administration

  • Adhesive patches – pain control, nitroglycerine patches, hormones, birth control patches, nicotine patches

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Eye, Ear and Nose Drops

Drops written as gtts

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Rectal Suppositories

  • Excellent route of administration of medications for the client that is:

    • Vomiting / nausea

    • Refuses to take medication PO

    • Difficulty swallowing a medication

    • Infants – fever or pain medications

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Topical Applications

  • Sunscreen

  • Antibiotic ointments

  • Cortisone

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  • Transportation of drug molecules within the body after the drug is absorbed into the blood stream.

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  • Drug needs to be carried to the site of the action.

    • Carried by the blood and tissue fluids to the sites of pharmacological action.

    • Distribution depends on adequacy of blood circulation.

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Key Concepts of Distribution

  • Protein binding – drug molecules need to get from the blood plasma into the cell.

  • Protein binding allows part of the drug to be stored and released as needed.

  • Some of the drug is stored in muscle, fat and other body tissues and is gradually released into the plasma.

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Just how does the drug get into the cell?

  • Drug must pass though the capillary wall

  • Blood brain barrier – very effective in keeping drugs from getting into the central nervous system or CNS – limits movement of drug molecules into brain tissue

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  • Method by which the drugs are inactivated or biotransformed by the body.

  • Most drugs metabolized in the liver by cytochrome P450 (CYP) enzyme.

  • Hepatic drug metabolism or is major mechanism for terminating drug action and eliminating drugs from the body.

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What can stop this process?

  • Enzyme inhibition

    • Other drugs

    • Combination drugs

    • Liver disease

    • Impaired blood circulation in person with heart disease

    • Infant with immature livers

    • Malnourished people or those on low-protein diets

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An important concept!

  • First-pass effect – some drugs are extensively metabolized or broken down in the liver and only a part of the drug is released into the systemic circulation

  • This is why dosage is important – how much drug needs to be taken in to give the desired effect and how often does it need to be taken

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  • Refers to the elimination of the drug from the body.

  • Requires adequate functioning of the circulatory system and organs of excretion.

    • Kidneys via urine

    • Liver via bile and into the feces

    • Lungs via exhaled air

    • Saliva, tears and sweat or skin

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Important concepts

  • Absorption – small intestine, skin, rectal or vaginal tissue

  • Metabolism – liver

  • Distribution – circulation (blood or plasm)

  • Excretion – urine, stool, skin

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Dosing Schedules

  • Determined by drug’s pharmacokinetic properties

    • Route of administration

    • Onset of action

    • Peak concentration level

    • Duration of action

    • Half-life

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Onset of action

  • The time when the drug’s effects first become noticeable.

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Peak Concentration

  • Maximum blood concentration level achieved through absorption; at this level most of the drug reaches the site of action and provides therapeutic response.

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  • Duration of action: the length of time a drug acts on the body.

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  • The time required for a drug’s plasma concentration to decrease to 50%.

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  • Study of what the drug does to the body.

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  • Therapeutic effect: the clinical indication for administering the drug.

    • Prevent disease

    • Treat disease

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  • Immunizations

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Treat Disease

  • Acute therapy

  • Maintenance therapy

  • Supplemental therapy

  • Palliative therapy

  • Supportive therapy

  • Prophylactic therapy

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Acute Therapy

  • Intensive drug therapy implemented in acutely ill clients

  • Often used to sustain life or treat disease

    • ICU

    • Emergency Treatment

    • Cardiac Resuscitation

    • Septic shock – IV antibiotics

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Maintenance Therapy

  • Prevent progression of the disease

    • Insulin for diabetes

    • Anti-hypertensive drugs to control hypertension or high blood pressure

    • Control chronic illness

    • Cholesterol control

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Palliative Therapy

  • Make client as comfortable as possible

    • Pain control in cancer clients

    • Oxygen for client with pulmonary disease

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Supportive Therapy

  • Maintains integrity of body functions while client is recovering from illness or trauma

    • Intravenous fluids to prevent dehydration

    • Blood for anemia or blood loss

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Prophylactic Therapy

  • Given to prevent illness or infection

    • Antibiotics prior to dental surgery

    • Antibiotics prior to orthopedic procedure

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Most important job of the nurse!

  • Monitoring the patient for effectiveness of therapy.

  • Response to medication needs to be evaluated.

  • Did the medication work!

  • Monitor for adverse effects

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Adverse Drug Reaction

  • Adverse drug reaction ADR: refers to unwanted or potential harmful effects of a drug; all drugs have one or more adverse reactions in addition to having the desired effect.

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Classification of Adverse Reactions

  • Drug related reactions

  • Sensitivity-related reactions

    • Hypersensitivity

    • Anaphylaxis

  • Toxicity

  • Unexpected or peculiar response to a drug

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  • Drugs can interact with other drugs or food.

  • In the drug history always ask about OTC and herbal therapy that may interact with prescribed medications.

  • Always check to seen when medication should be taken

    • With food

    • Before meals

    • After meals

    • Specific foods that may need to be avoided