Notes: Introduction to Drugs (Ch. 1-5) – Wolters Kluwer Transcript

Pharmacology: Key Concepts

  • Pharmacology is the study of the biological effects of chemicals.
  • Drugs are chemicals introduced into the body to cause a change.
  • Health care providers focus on how chemicals act on living organisms; nurses deal with pharmacotherapeutics (clinical pharmacology).
  • Drug effects can be therapeutic (beneficial) or adverse (undesirable or potentially dangerous).
    • Therapeutic effects
    • Adverse effects

Nurse Responsibilities

  • Administering drugs
  • Assessing drug effects
  • Intervening to make regimens more tolerable
  • Providing patient teaching about drugs and regimens
  • Monitoring the overall patient care plan to prevent medication errors and handle changes in therapy; if a drug is not continually assessed, talk to the physician about adverse effects and potential changes
  • If a med error occurs, report it

Sources of Drugs

  • Natural sources – Plants
  • Animal sources – Used to replace human chemicals not produced due to disease or genetic problems; genetic engineering advances; many preparations now created synthetically
  • Inorganic compounds – Salts of various elements can have therapeutic effects in the body (examples listed include insulin, magnesium, iron)
  • Synthetic sources – Genetic engineering can alter bacteria to produce therapeutic chemicals; original prototypes included in WWII-era Germany for painkiller development

Drug Evaluation and Development (Overview)

  • Preclinical trials – chemicals tested on laboratory animals
  • Phase I studies – chemicals tested on human volunteers
  • Phase II studies – drug tested on informed patients with the disease
  • Phase III studies – drug used in a broad clinical market
  • Phase IV studies – continual evaluation of the drug after approval
  • Note: Early examples in slides include “diphenhydramine” era and iterative evaluation; ongoing post-marketing evaluation is emphasized

Pregnancy Categories (FDA)

  • Five categories indicate potential for birth defects in systemically absorbed drugs; the categories reflect documentation quality and risk–benefit ratio
  • Category A: Adequate studies in pregnant women show no fetal risk in first trimester and no evidence of risk later
  • Category B: Animal studies show no risk; or there are no adequate human studies but no fetal risk in the first trimester
  • Category C: Animal studies show adverse effects; no adequate human studies; benefits may outweigh risks, or there are no animal studies and no adequate human studies
  • Category D: Evidence of fetal risk in humans; potential benefits may justify use
  • Category X: Fetal abnormalities or adverse reactions; risk clearly outweighs any potential benefit
  • Important caution: Regardless of category, no drug should be administered during pregnancy unless clearly needed

Controlled Substances

  • The Controlled Substances Act (CSA) of 1970 – Drug control and enforcement coordinated by the FDA and DEA (Drug Enforcement Administration, U.S. Department of Justice)
  • Prescription, distribution, storage, and use are tightly regulated
  • Local policies and procedures may be more rigorous

Generic Drugs

  • Chemicals produced by companies that specialize in drug manufacturing
  • Bioavailability considerations are crucial for some drugs
  • “Dispensed as written” is important for drugs with narrow safety margins
  • Tests often assume drugs will be in generic form; expect generic nomenclature on exams

Over-the-Counter (OTC) Drugs

  • Available without prescription for self-treatment of a variety of complaints
  • Some OTCs were originally prescription drugs; others grandfathered as safe for broad use
  • Example: loratadine (Claritin) discussed as OTC
  • Nurse considerations with OTCs:
    • OTCs can mask signs/symptoms of underlying disease, delaying proper diagnosis
    • Interactions with prescription meds can occur
    • Incorrect use can lead to serious overdoses

Sources of Drug Information

  • Drug Label – contains specific, essential information about a drug; learning to read labels is critical
  • Package Insert – prepared by the manufacturer; contains chemical and study information that supported approval; often difficult to read
  • Reference Books – PDR, Drug Facts and Comparisons, AMA Drug Evaluations, Lippincott’s Nursing Drug Guide (LNDG)
  • Journals
  • Internet – many sources are online; verify reliability

Example Product: AUGMENTIN® (Amoxicillin/Clavulanate)

  • Reconstitution directions illustrate typical label details:
    • Amoxicillin 125 mg per 5 mL suspension; clavulanic acid 31.25 mg per 5 mL
    • After reconstitution, total volume ~75 mL
  • Directions involve sequence for adding water, shaking, and storage conditions:
    • Tap bottle to flow freely, add ~2/3 total water, shake, add remaining water, shake again
    • Dose: See prescribing information
  • Label notes include:
    • Tear along perforation, keep tightly closed, shake well before using
    • Must be refrigerated; discard after 10 days
  • Manufacturer data and NDC (national drug code): extNDC=0029−6085−39ext{NDC} = 0029-6085-39
  • Brand/generic labeling and shelf-life details are common in package inserts

Sources of Drug Information (Cont.)

  • Reference Books (examples): Physician’s Drug Reference (PDR), Drug Facts and Comparisons, AMA Drug Evaluations, Lippincott’s Nursing Drug Guide (LNDG)
  • Journals and Internet sources also used for current information

Pharmacokinetics: Core Concepts

  • Critical concentration – the amount of a drug needed to produce a therapeutic effect
  • Loading dose – a higher dose used to rapidly achieve therapeutic levels
  • Dynamic equilibrium – actual concentration achieved at the site; influenced by absorption and distribution
  • Absorption, distribution, metabolism (biotransformation), and excretion determine overall pharmacokinetics
  • Key processes: absorption, distribution, metabolism, excretion; the acronym ADME

Drug Action and Receptor Sites

  • Receptor sites respond to chemicals to produce cellular effects
  • Agonists – activate receptor sites to produce an effect
  • Antagonists – block receptor sites and prevent agonist binding
    • Competitive antagonism – competes for the same receptor site as the agonist
    • Noncompetitive antagonism – binds to a different site but blocks the receptor’s function
  • Drug–enzyme interactions and selective toxicity – drugs target specific cellular processes while minimizing harm to host cells
  • Lock-and-key illustration concepts:
    • Drug A (agonist) binds to receptor and produces effect
    • Drug B cannot bind and produces no effect
    • Competitive antagonists (Drug C) bind the same site and block Drug A
    • Noncompetitive antagonists (Drug D) bind a different site and prevent Drug A binding

Absorption

  • Definition: the process by which a drug moves from administration site into circulating fluids
  • Routes of administration influence absorption
  • Oral medications: absorption affected by presence of food in stomach
  • Mechanisms: passive diffusion and active transport

Distribution

  • Movement of a drug to tissues; depends on:
    • Lipid solubility and ionization (affects blood-brain barrier and tissue penetration)
    • Perfusion of the tissue
    • Placenta/Breast milk distribution (lipid-soluble drugs penetrate more readily; ionized/hydrophilic forms penetrate less easily)

Biotransformation (Metabolism)

  • Liver is the primary site of biotransformation (metabolism)
  • Functions:
    • Breaks down medications
    • Helps prevent adverse effects from drugs
    • First-pass effect (high initial metabolism reduces bioavailability for some oral drugs)

Excretion

  • Removal of drugs from the body
  • Kidneys play the most important role in excretion
  • If kidneys are affected, drug excretion may be impaired, leading to accumulation

Half-Life

  • Definition: the time it takes for the amount of drug in the body to decrease to one-half its peak level
  • Influenced by absorption, distribution, metabolism, and excretion
  • Often a focus of exam questions asking to compute clearance or dosing intervals

Factors Influencing Drug Effects

  • Weight
  • Age
  • Gender
  • Physiological factors
  • Pathological factors
  • Food intake
  • Genetic factors
  • Immunological factors
  • Psychological factors
  • Environmental factors
  • Drug tolerance
  • Cumulative effect
  • Other drugs (drug–drug interactions)

Adverse Drug Reactions (ADRs)

  • Undesired effects that may be unpleasant or dangerous
  • Reasons ADRs occur:
    • Drug may have effects beyond the therapeutic purpose
    • Patient sensitivity to the drug
    • The drug’s action may cause other, undesired responses
    • Dosing issues (too much or too little)

Types of Adverse Reactions

  • Primary actions – overdose or extension of the desired effect
  • Secondary actions – undesired effects produced in addition to the pharmacologic effect
  • Hypersensitivity reactions – excessive response to primary or secondary effects

Drug-Induced Tissue and Organ Damage

  • Examples include ocular toxicity (eye damage, visual changes, peripheral vision loss) and auditory damage (hearing loss)

Dermatological Reactions

  • Rash/hives – assessment and possible discontinuation in severe cases
  • Stomatitis – mucous membrane inflammation; oral care and airway considerations may be necessary

Superinfections and Blood Dyscrasia

  • Superinfections – destruction of normal flora; symptoms include fever, diarrhea, vaginal discharge; interventions include supportive care and antifungal use; may require stopping the drug
  • Blood dyscrasia – bone marrow suppression; symptoms: fever, chills, weakness; interventions include monitoring blood counts and protective isolation; antibiotics as needed

Neurological and Other Effects

  • CNS effects – assessment of altered level of consciousness; interventions focus on injury prevention
  • Anticholinergic (Atropine-like) effects – dry mouth, urinary retention, blurred vision; interventions include sugarless lozenges and ensuring voiding prior to administration

Teratogenicity

  • Teratogenicity: any drug causing harm to the developing fetus or embryo
  • Counseling to prevent teratogenicity:
    • Advise pregnant patients that any medication may affect the baby
    • Weigh benefits against potential risks
    • Do not take medications without consulting a health care provider

Nursing: Art and Science

  • Nursing is expanding responsibilities
  • Holistic approach; nurses are key health care providers
  • Integrates knowledge from basic sciences, social sciences, education, and other disciplines
  • Applies the nursing process

Nursing Process

  • Assessment – data gathering (history, physical assessment, holistic view)
  • Nursing Diagnosis – conclusions drawn from assessment data
  • Planning/Implementation – creating a plan of care to improve or maintain health
  • Evaluations – determine effectiveness of the plan

Patient and Family Education

  • Cornerstone of drug therapy
  • Nurses are the primary educators about medications

Challenges to Effective Drug Therapy in the 21st Century

  • Greater access to medical and pharmacological information from multiple sources
  • Consumers increasingly demand specific treatments and consider alternatives
  • Alternative therapies advertised and offered
  • Financial pressures lead to earlier discharge; emphasis on patient teaching and home care

Federal Guidelines – Drug Advertising

  • Advertisements must include indications, contraindications, adverse effects, and precautions

Consumer Awareness and Internet Sources for Drug Information

  • Pharmaceutical company information sites
  • Online discussions and chat rooms with other patients
  • Online pharmacies
  • Lists of government regulations and research reports
  • Internet can aid or mislead; verify reliability

OTC Medications: Issues and Considerations

  • OTCs can mask underlying disease, interact with prescriptions, and cause toxicity if misused
  • Some medications were grandfathered; others became OTC after safety evidence
  • Important to avoid exceeding recommended doses

Alternative Therapies and Herbal Medicine

  • Active ingredients may not be FDA-tested; incidental ingredients are often unknown
  • Patients may not disclose use to health care providers; possible drug–alternative therapy interactions
  • CBD and other herbs discussed as examples

Controls for Alternative Therapies

  • Herbal medications and other alternative therapies are not regulated or tested by the FDA
  • Advertising for these products is less restricted because they are treated as dietary supplements
  • No broad regulatory oversight in the same way as conventional drugs

Off-Label Medications

  • Definition: use of a drug for an indication not approved by the FDA
  • Occurrence: common in populations with little premarketing testing, especially pediatric and geriatric groups
  • Examples (from slides): diphenhydramine used for sleep despite other indications

Closing Notes

  • The material emphasizes the interconnected nature of pharmacology knowledge: pharmacokinetics, pharmacodynamics, patient safety, regulatory frameworks, and professional nursing roles.
  • Understanding these topics supports safe, effective medication administration and patient education.