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Pharmacology Review

Unit 1 Core Concepts In Pharmacology

Chapter 1: Introduction to Pharmacology

  • Topics Covered:
    • Drug classification
    • Drug names (chemical, generic, trade)
    • Prescription vs. OTC drugs
    • Differences between trade-name drugs and generic equivalents

1.4 Classification of Therapeutic Agents

  • Drug: A chemical agent capable of producing biologic responses.
    • Responses can be desirable (therapeutic) or undesirable (adverse).
  • Medication: A drug after it is administered.
  • Biologic Agents:
    • Naturally produced in animal cells, microorganisms, or by the body itself.
    • Examples: hormones, monoclonal antibodies, blood products.
  • CAM Therapy (Complementary Alternative Medicine):
    • Examples: plant extracts, vitamins, herbs, physical therapy, acupuncture.

1.5 Therapeutic and Pharmacologic Classification of Drugs

  • Therapeutic Classification:
    • Example: Antihypertensive (lowers BP).
  • Pharmacologic Classification:
    • Example: Non-selective Beta Blocker.
  • Mechanism of Action:
    • Example: Blocks activation of B1 and B2 receptor sites.
  • Examples:
    • Carvedilol (Coreg):
      • Therapeutic: Antihypertensive.
      • Pharmacologic: Non-selective Beta Blocker.
      • Mechanism: Blocks activation of B1 and B2 receptor sites.
    • Diltiazem (Cardizem):
      • Therapeutic: Antihypertensive, Antianginal, Antidysrhythmic.
      • Pharmacologic: Calcium Channel Blocker.
      • Mechanism: Inhibits calcium influx into arterial smooth muscle and myocardial tissue; affects cardiac action potential.

1.5 Prototype Drug

  • Prototype Drug: An individual drug that represents a drug class.
    • Drugs within the same class share similar chemical structures, mechanisms of action, and modes of action.
    • The prototype is the most important drug within a class; used as a reference for comparison.
    • Example: Nitroglycerin (Nitrostat, Nitro-Bid, Nitro-Dur).

1.6 Chemical, Generic, & Trade Names

  • Multiple trade names can exist for a single drug, but there is only one generic name.
  • Organizations like the FDA, USP, and WHO prefer the use of generic names.
  • Example: Ibuprofen has one generic name (ibuprofen) but multiple trade names.

1.7 Prescription vs OTC Drugs

  • Prescription Drugs:
    • Require a doctor's prescription.
    • Purchased from a licensed pharmacy.
    • For the use of a specific patient.
    • Require a medical diagnosis.
    • Stronger than OTC drugs.
    • Used to treat major diseases (e.g., diabetes, heart diseases).
    • Expensive.
    • Covered by insurance companies.
  • OTC Drugs:
    • Do not require a prescription (e.g., aspirin, antacids).
    • Purchased from any store.
    • Could be used by multiple patients.
    • Rely on self-diagnosis.
    • Milder drugs with a wide margin of safety.
    • Used to treat minor diseases (e.g., headaches, cold and coughs).
    • Less expensive than prescription drugs.
    • Not covered by insurance companies.

1.8 Differences Between Trade-Name Drugs & Their Generic Equivalents

  • Bioavailability: The physiologic ability of the drug to reach its target cells and produce a specific effect.
    • Even if dosages are identical, drug formulations may differ.
    • Bioavailability can be affected by differing inert ingredients and tablet compression techniques between brand and generic drugs.

Chapter 2: Drug Approval and Regulation

  • Focus on regulations and standards.
  • Role of the FDA, including Black Box Warnings.
  • DEA drug schedules and teratogenic risks.

2.1 Drug Regulations & Standards

  • U.S. Pharmacopoeia (USP): First published in 1820.
  • National Formulary (NF).
  • National Drug Code (NDC).
  • Since 1906, laws have been passed to create uniform drug standards to ensure the quality, regulation, and safety of drugs.

2.2 The Role of the FDA

  • Black Box Warnings (1997):
    • Flagging important safety information.
    • Most serious medication warning required by the FDA.
    • Used when a medication can cause serious undesirable effects compared to the potential benefit.
    • Indicates need for extra precautions.
    • A Black Box warning doesn't indicate that a drug is too dangerous to use; it means maximum precaution must be taken.
  • DEA Schedule: (refer to drug schedule chart)

2.6 Controlled Substances, Drug Schedules, and Teratogenic Risks

  • Drug Schedules (Table 2.4):

    • Schedule I: Highest potential for abuse; limited or no therapeutic use.
    • Schedule II: High potential for abuse; used therapeutically with prescription.
    • Schedule III: Moderate potential for abuse; used therapeutically with prescription; some drugs no longer used.
    • Schedule IV: Lower potential for abuse; used therapeutically with prescription.
    • Schedule V: Lowest potential for abuse; used therapeutically without prescription.

  • FDA Pregnancy Categories:

    • Category A: Controlled studies show no risk to the fetus.
    • Category B: No evidence of risk in humans.
    • Category C: Risk cannot be ruled out; potential benefits may justify potential risk.
    • Category D: Positive evidence of risk to the fetus; potential benefits may outweigh risks.
    • Category X: Contraindicated in pregnancy; fetal risk clearly outweighs any possible benefit.

Chapter 3: Principles of Drug Administration

  • Focuses on responsibilities of the RN, legal aspects of drug orders, and rights of drug administration

Responsibilities of the RN

  • TIME, PATIENT, ROUTE, DRUG

3.1 Medication Knowledge and Understanding

  • A major goal of studying pharmacology is to limit the number and severity of adverse drug events.
  • The RN must have comprehensive knowledge of the actions and side effects of any drug before administration.

The Four Most Common Medication Errors

  • Errors in patient assessment (e.g., inadequate medication history).
  • Errors in prescribing (e.g., wrong drug or incorrect dose).
  • Administration errors (e.g., wrong route or time).
  • Distracting environmental factors (e.g., interruptions during preparation).

The 8 Parts of A Legal Drug Order

  • Name of the patient
  • Name of the drug to be administered
  • Dosage of the drug
  • Route of administration
  • Frequency, time, and special instructions
  • No unapproved abbreviations
  • Date and time when the order was written
  • Signature and licensure of the person writing the order
  • If any part is missing or unclear, the order is incomplete and the drug should not be given.
  • Example: “Give patient John Smith aspirin (Ecotrin) 81 mg PO once a day. Dr. Billy Rubin, MD August 1, 2022 at 1500”

The RN is responsible for knowing:

  1. Generic Name
  2. Trade Name
  3. Classification
  4. Route
  5. Ordered Dose
  • Additional Responsibilities:
    • Indication: Why is the patient receiving this medication?
    • Mechanism of Action: How does this medication work?
    • Common Side Effects
    • Common Adverse Effects
    • Nursing Responsibilities; Contraindications
    • Patient Teaching

Anaphylaxis and Allergic Reaction

  • It is vital that the RN be prepared to recognize and respond to the potential harmful effects of medication.
  • Side Effect
  • Adverse Effect
  • Allergic Reaction: An acquired hypersensitivity to a foreign substance.
    • If discovered, the RN is responsible for documentation, labeling charts, informing healthcare personnel, and placing an alert bracelet on the patient.
  • Anaphylaxis: A severe allergic reaction involving the massive, systemic release of histamine and other chemical mediators of inflammation that can lead to life-threatening shock.
  • Stevens Johnson Syndrome

3.2 The Eight Rights of Drug Administration

  1. Right patient: Use of 2 identifiers.
  2. Right medication: Check the pill identifier.
  3. Right dose: Confirm appropriateness of the dose using a current drug reference.
  4. Right route: Confirm that the patient can take or receive the medication by the ordered route.
  5. Right time: Confirm when the last dose was given and safe window of administration
  6. Right documentation: Chart the site of an injection or any laboratory value or vital sign that needed to be checked before giving the drug.
  7. Right reason: Revisit the reasons for long-term medication use.
  8. Right response: Document monitoring of the patient and nursing interventions.

Drug Administration

  • Verify medication order, check allergy history
  • Wash hands
  • Use aseptic technique when preparing and administering parenteral medications
  • Identify patient (two forms of ID)
  • Ask patient about known allergies
  • Tell the patient about the drug
  • Position the patient for safe swallowing
  • Remove prepackaged drugs at the bedside, showing them to the patient as you go
  • Apply gloves, if indicated
  • Do not leave drugs at bedside

3.6 Enteral Drug Administration

  • The enteral route includes tablets, capsules, sublingual and buccal drugs administered by mouth, NGT, or GT
  • Tablets can be crushed or cut, and capsules opened, only with manufacturer approval
  • Enteric-coated tablets must remain intact
  • Sustained-release tablets or capsules are designed to dissolve very slowly

Parenteral Drug Administration

  • Includes intravenous (IV) administration.

Intravenous (IV) Administration

  • Medications and fluids are administered directly into the bloodstream and are immediately available for use by the body
  • Fastest drug onset action, but also most dangerous method
  • Risk for contamination
  • Can result in swift adverse reactions

Parenteral Advantages and Disadvantages

  • Advantages:
    • Bypasses first-pass effect
    • Available to patients unable to take medication orally
  • Disadvantages:
    • Possible pain, infiltration, and swelling at IV site

IV Complications

  • Infection at the IV site:
    • Occurs due to failure to use aseptic technique during IV insertion or to follow hospital policy.
    • Localized symptoms: redness, pain, swelling, or skin breakdown.
    • Systemic symptoms: fever.
  • Infiltration:
    • Occurs when the IV catheter becomes dislodged from the vein and IV fluid escapes into the subcutaneous tissue.
    • Symptoms: Cool and puffy skin.
  • Phlebitis:
    • Occurs when the vein becomes irritated from certain medications in the IV solution.
    • Symptoms: Red, warm, and cord-like vein, often painful.

Chapter 4: Pharmacokinetics

  • How drugs move through the body.

Biological Processes in Pharmacokinetics

  1. Absorption:
    • The movement of a drug from its site of administration into circulation.
  2. Distribution:
    • The dispersion of the drug from the bloodstream into other tissues and organs of the body.
  3. Metabolism (also called biotransformation):
    • The biological alteration of drug molecules that facilitates excretion and that may stop their pharmacological effects.
  4. Excretion:
    • The clearance of drug molecules and their metabolites from the body.

4.1 Pharmacokinetics: How the Body Handles Medications

  • Pharmacokinetics: the study of drug movement throughout the body
  • Knowing the pharmacokinetics of a drug helps the RN to understand and predict actions and side effects of medications
  • Understanding how a drug affects target cells enables the RN to assess if the prescribed medication route is safe and effective

4.3 Absorption of Medications

  • Absorption: How a drug gets from its route of administration into the bloodstream (systemic circulation).
  • Bioavailability: The percentage of drug absorbed into the systemic circulation.

Bioavailability & Drug Absorption

  • Drug absorption of various preparations from fastest to slowest:
    • Liquids, elixirs, and syrups.
    • Suspension solutions.
    • Powders.
    • Capsules.
    • Tablets.
    • Coated tablets.
    • Enteric-coated tablets.

Factors Adversely Affecting Drug Absorption

  • Decreased gastric acid production (pH)
  • Decreased GI motility
  • Prolonged gastric emptying
  • Excessive ETOH use

4.4 Distribution of Medications

  • Distribution: How a drug gets from the systemic circulation to its target site.

Medication Distribution

  • Oral drug goes through the following steps:
    • Oral drug taken by patient.
    • Drug absorbed across the intestinal mucosa.
    • Drug enters portal circulation and travels to the liver.
    • On first pass through the liver, drug is metabolized to less active forms.
    • Drug metabolites leave the liver for distribution to tissues.
    • To heart and systemic circulation

Factors Adversely Affecting Medication Distribution

  • Dehydration
  • Low albumin levels
  • Decreased cardiac output
  • Decreased peripheral blood flow
  • Increased or decreased percentage of body fat

4.5 Metabolism of Medications

  • Metabolism: Refers to the breakdown of a drug to a less active form by enzymes in the liver, in preparation for it to be excreted from the body.
  • Also known as “biotransformation”.

4.5 First-Pass Effect of PO Meds

  • Drug enters the hepatic circulation & goes to liver
  • Drug is metabolized to a less active or concentrated form
  • Drug is then distributed through the general circulation

Grapefruit Juice

  • Grapefruit contains furanocoumarins which can interfere with drug metabolism
  • Enzyme blocked, leading to too much drug in the body.

Factors Adversely Affecting Drug Metabolism

  • Dehydration
  • Liver dysfunction
  • Decreased cardiac output
  • Decreased hepatic and intestinal blood flow

4.5 Excretion of Medications

  • Excretion: The removal of drugs and their metabolites from the body, most often through the kidneys.

4.6 Excretion of Medications

  • Free drugs, water-soluble agents, electrolytes, and small molecules are easily filtered
  • Drug-protein complexes and large substances are secreted into the distal tubule of the nephron
  • Secretion mechanisms are less active in infants and older adults
  • pH of filtrate can influence excretion
  • Drugs are retained for extended times
  • Dosages must be reduced

Factors Adversely Affecting Drug Excretion

  • Renal dysfunction
  • Pre-renal effects
  • Intra-renal effects

4.7 Drug Plasma Concentration and Therapeutic Response

  • The concentration of the medication at the target tissue site is often impossible to measure, so it must be measured by way of plasma drug concentrations
  • Minimum effective concentration—minimum amount of drug required to produce a therapeutic effect
  • Toxic concentration—level of drug that will result in serious adverse effects
  • Therapeutic range—plasma drug concentration between the minimum effective concentration and the toxic concentration

4.8 Onset, Peak Levels, & Duration of Drug Action

  • An Example of A Single-Dose Drug Administration
  • Pharmacokinetic values for this drug are as follows:
    • Onset of action = 2 hours
    • Time to peak drug effect = 5 hours
    • Duration of action = 6 hours
    • Termination of action = 8 hours after administration

Half-Lives & Steady States

  • The half-life of a drug is the time it takes for 1/2 of the original amount of the drug in the body to be removed or excreted.
    • For example, a drug dose of 100 mg is given. In 8 hours the blood level of the drug is now 50 mg. Thus, the estimated half life of this drug is 8 hours.
  • Steady state blood levels refer to a physiologic state in which the amount of drug removed via elimination is equal to the amount of drug being absorbed with each dose.

Chapter 5: Pharmacodynamics

  • How drugs affect the body.

5.6 Types of Drug-Receptors

  • A) Drugs act by forming a chemical bond with specific receptor sites, similar to a key and lock.
  • B) The better the “fit,” the better the response. Those with complete attachment and response are called agonists.
  • C) Drugs that attach but do not elicit a response are called antagonists.
  • D) Drugs that attach, elicit a small response, and also block other responses are called partial agonists or agonist-antagonists.

Effects of Drug Interactions

  • Synergistic (aka potentiated) drug effects:
    • An interaction between two or more drugs that causes the total effect of the drugs to be greater than the individual effects of each drug.
    • Example: Valium and ETOH
  • Antagonistic drug effects:
    • When one drug decreases or abolishes the action of another.
    • Example: Morphine and Narcan