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