Pharmacology Chapter 5

Housekeeping

• Registration
• Review of syllabus and expectations
• Kaplan review
• Importance of learning generic drug names for the NCLEX exam
• Questions

Pharmacological Principles

• Pharmaceutics
• Pharmacokinetics
• Pharmacodynamics
• Pharmacogenomics
• Pharmacotherapeutics

Pharmaceutics

• Study of how various drug forms influence the way a drug affects the body
• Dissolution
  • SR (sustained release)
  • SA (sustained action)
  • CR (controlled release)
  • XL (extended release)
  • XT (extended time)
  • Thin-film

Phases of Drug Activity

• Pharmaceutical phase
  • Disintegration and dissolution of the drug
• Pharmacokinetic phase
  • Absorption, distribution, metabolism, excretion
• Pharmacodynamic phase
  • Drug-receptor interaction

Pharmacokinetics

• Study of what the body does to the drug
  • From the time the drug is administered until the parent drug and metabolites leave the body
• Absorption
• Distribution
• Metabolism
• Excretion

Absorption

• Bioavailability
• Bioequivalent
• First-pass effect
• Enteral route
  • Sublingual
  • Buccal
  • Oral
  • Nasogastric, g-tube, j-tube
  • Rectal
• Parenteral route
  • Intradermal
  • Subcutaneous
  • Intravenous (IV) - 100% bioavailability
  • Intramuscular
  • Intrathecal
  • Intra-articular
  • Intra-arterial
• Topical route
• Transdermal route
• Inhalation route

Distribution

• Transport of a drug by the bloodstream to the drug's site of action
• Drugs distributed first to areas with extensive blood supply
  • Heart, liver, kidneys, and brain
• Protein binding
  • Albumin is the most common blood protein and carries most protein-bound drug molecules
  • If a drug binds to albumin, only a limited amount is unbound
  • Unbound portion or "free" drug is active
  • Certain conditions lead to low albumin, increasing the chance of toxicity
  • Drug interactions can occur if drugs fight to bind
  • Blood-brain, blood-placenta barriers

Metabolism

• Also referred to as biotransformation
• Biochemical alteration of the drug into any of the following:
  • Inactive metabolite
  • More soluble compound
  • More potent metabolite (as in the conversion of an inactive prodrug to its active form)
  • Less active metabolite
• Hepatic metabolism
  • Cytochrome P-450 enzymes (AKA microsomal enzymes)
    • Lipophilic ("fat loving")
    • Hydrophilic ("water loving")
  • Substrates - drug molecules that are targets for enzyme
  • Enzyme inhibitors (meds delay metabolism) - e.g., erythromycin
  • Enzyme inducers (speed up metabolism) - e.g., phenytoin

Excretion

• Elimination of drugs from the body
• Primary organ responsible is the kidney
• Liver and bowel also play a role
• Renal excretion
• Biliary excretion

Other Pharmacokinetics Terms

• Half-life
• Steady state
• Onset of action
• Peak effect
• Duration of action

Pharmacodynamics

• The study of what the drug does to the body
• Mechanism of drug actions in cells and tissues
• Therapeutic effect
• Goal of drug therapy
• Mechanism of action (MOA)
• Receptor interactions
• Enzyme interactions
• Nonselective (chemo)

Pharmacotherapeutics

• Clinical use of drugs to prevent and treat diseases
• Desired therapeutic outcomes are patient-specific, established in collaboration with the patient
• Outcome goals need to be realistic
• Types of Therapy
  • Acute
  • Maintenance
  • Supplemental
  • Palliative
  • Supportive
  • Prophylactic
  • Empirical
• Monitoring
  • Therapeutic action
  • Beneficial effects
  • Adverse drug event
  • Adverse drug reaction
  • Toxic effects
  • Therapeutic index (low = small gap between therapeutic and toxic)
  • Drug concentration
  • Patient condition
• Tolerance
• Dependence
  • Physical dependence
  • Psychological dependence
• Drug interactions
  • Additive effects (1 + 1 = 2)
  • Synergistic effects (1 + 1 > 2)
  • Antagonistic effects (1 + 1 < 2)
  • Incompatibility (1 + 1 = 0)
• Other drug effects
  • Teratogenic
  • Mutagenic
  • Carcinogenic
• Ten Rights of Medication Administration
  • Right drug
  • Right dose
  • Right time
  • Right route
  • Right patient
  • Right reason
  • Right documentation
  • Right evaluation for right assessment
  • Right patient education
  • Right to refuse

Over-the-Counter Drugs

• Nonprescription drugs
• Use for short-term treatment of common minor illnesses.
• More than 40,000 OTC drugs available in Canada
• Regulated by Health Canada's Food and Drug Regulations
• Safety and efficacy
• Appropriate labelling standards
• Reclassification
• Most common OTCs in Canada?

Over-the-Counter Status Criteria

• Indications for Use
  • Consumer must be able to easily diagnose and monitor condition
  • Benefits of correct usage must outweigh risks
• Safety Profile
  • Favorable adverse event profile
  • Limited interaction with other drugs
  • Low potential for misuse
  • High therapeutic index
• Practicality for OTC Use
  • Easy to use
  • Easy to monitor

Reclassified OTC Drugs

• Analgesics
  • Acetaminophen, codeine, caffeine
  • Acetylsalicylic acid, codeine, caffeine
  • Ibuprofen
  • Naproxen sodium
• Histamine blockers
  • Cetirizine
  • Chlorpheniramine maleate
  • Diphenhydramine hydrochloride
  • Loratadine
• H₂-receptors
  • Famotidine
  • Ranitidine
• Proton pump inhibitors
  • Omeprazole and esomeprazole
• Smoking Deterrents
  • Nicotine gum
  • Nicotine Transdermal patch
• Topical Medications
  • Clotrimazole
  • Miconazole nitrate
  • Minoxidil

Possible Drug Interactions

• Herbs and other natural products interactions

Nursing Implications

• Provide thorough and individualized patient education.
• Ensure patients recognize that manufacturers of herbal products and dietary supplements are not required to prove safety and effectiveness.
• Herbal products may not be safe for infants, children, or pregnant or lactating women.
• Natural does not mean safe.
• Teach patients to monitor themselves for unusual or adverse reactions as well as therapeutic responses
• Obtain thorough medication history, documenting all medications used.
• Assess level of education and understanding, information specific to various products, system functions (renal, liver, cardiac), conditions that are contraindications, potential drug-drug and drug-food interactions

Case Studies

• Herbals and Cardiovascular Disease
• St. John's Wort and Serotonergic Drugs
• Ginkgo and Anticoagulants

Homeopathy

• Form of alternative medicine
• Based on the belief a disease can be treated by the administration of a microdose of a substance thought to cause the physical signs of that disease
• Thought to stimulate the body's immune defenses
• No quality peer-reviewed evidence to support

Vitamins and Minerals Overview

• Body needs essential building blocks to grow and maintain itself
• Carbohydrates
• Fats
• Proteins
• Vitamins and minerals
• Enzymes and coenzymes

Vitamins

• Organic molecules needed in small quantities for normal metabolism and other biochemical functions
• Attach to enzymes or coenzymes and help them activate anabolic processes
• Natural sources from both plants and animals
• Insufficient amounts result in various deficiencies
• Labelled as NHPs in Canada
• Controversy about "megadosing"

Fat-Soluble Vitamins

• Present in both plant and animal foods
• Stored primarily in the liver and fatty tissue
• Exhibit slow metabolism or breakdown
• Excreted via the feces
• Can be toxic when consumed in excess
• Vitamins A, D, E, and K
• Deficiencies occur only after prolonged deprivation or from disorders that prevent their absorption
• Daily intake not required unless one is proven deficient
  • Vitamin A
  • Vitamin D
  • Vitamin E
  • Vitamin K

Water-Soluble Vitamins

• B-complex group and vitamin C
• Can be dissolved in water
• Easily excreted in the urine
• Cannot be stored by the body over long periods
• Daily intake in a balanced diet required to prevent deficiencies
  • Vitamin B complex
  • Vitamin C

Minerals

• Essential nutrients
• Inorganic compounds
• Bind with enzymes or other organic molecules
• Help to regulate many bodily functions such as muscle contraction and nerve transmission
• Building blocks for many body structures
• Required for intracellular and extracellular body fluid electrolytes
• Macro- and micro-minerals
  • Calcium
  • Magnesium
  • Phosphorus
  • Zinc

Wrap-up

• Questions?
• Next week: Anti-inflammatories, Anti-gout, Biologics, Antirheumatics