Paramedic Pharmacology: Pharmacokinetics

• Introduction to Paramedic Pharmacology at VVC Paramedic Academy

Pharmacokinetics

• Pharmacokinetics involves how drugs are transported into and out of the body
• Intensity and duration of a drug's effect depends on pharmacokinetics
• Pharmacokinetics relies on these four processes:
  • Absorption
  • Distribution
  • Biotransformation
  • Elimination

Absorption

• Describes the routes of administration and peak effects:
  • Intravenous: 30-60 seconds
  • Intraosseous: 30-60 seconds
  • Endotracheal: 2-3 minutes
  • Inhalation: 2-3 minutes
  • Sublingual: 3-5 minutes
  • Intramuscular: 10-20 minutes
  • Subcutaneous: 15-30 minutes
  • Rectal: 5-30 minutes
  • Ingestion: 30-90 minutes
  • Transdermal: variable (minutes to hours)

Diffusion and Osmosis

• Diffusion: Molecules move from high to low concentration; involves both solute and solvent
• Osmosis: Solvent moves across a semipermeable membrane from high to low solvent concentration; involves only the solvent

Distribution

• Drug distribution is affected by these factors:
  • Concentration of drug transporters in blood
  • pH
  • Perfusion
  • Body water composition
  • Body fat composition
  • Certain disease conditions

Blood-Brain Barrier

• Located in the CNS
• Cells are tightly packed, this only allows non-protein-bound, highly lipid-soluble drugs into the CNS

Placental Barrier

• Can prevent medications from reaching a fetus
• Delivery of drugs to a fetus requires drugs to be lipid soluble, nonionized, and non-protein bound

Biotransformation

• Its a series of processes that change substances' chemical structures.
• The enzymes that catalyze reactions may cause the substrate to become inactive, active, or even toxic.
• Most biotransformation processes occur in the liver.
• First-pass effect thru the liver can alter or inactivate the drug entirely.

Two effects of biotransformation on drugs

• Conversion of the drug into a more or less active form
• Increasing the drug's water solubility (or decrease its lipid solubility) to aid elimination

Elimination

• Occurs by renal excretion through two major processes:
  • Glomerular filtration
  • Results from blood pressure and blood flow through kidneys
  • Tubular secretion
  • Secretion and reabsorption
  • Tubule secretion can impact the drug speed elimination

Alternative elimination routes

• Breath, blood, sweat, saliva, and breast milk

Factors that affect medication elimination

• Liver function
• Blood pressure conditions
• Protein binding
• Urine pH
• Urine flow

Drug Routes

• Enteral Routes: Deliver medications via absorption through the GI tract, including
• Oral (PO)
• Orogastric (OG)
• Nasogastric (NG)
• Sublingual (SL)
• Buccal
• Rectal (PR)
• Parenteral Routes: Use needles to introduce medicine into the circulatory system or tissues, including:
  • Intravenous (IV)
  • Endotracheal (ET)
  • Intraosseous (IO)
  • Umbilical
  • Intramuscular (IM)
• Subcutaneous (SC)
• Inhalation/Nebulized
• Topical
• Transdermal
• Nasal
• Instillation
• Intradermal

Drug Forms

• Drug forms include capsules, pills, injections, sprays, dragees, syrups, suspensions, emulsions, granules, ointments, suppositories, gels, medical herbs, pastes, and tinctures, among others

Pharmacodynamics

• Involves the effect of drugs on the body
• The study involves molecular, biochemical, and physiologic effects or actions of a medication

Ways drugs can act

• Binding to the receptor site
• Changing the physical properties of cells
• Chemically combining with other chemicals
• Altering a normal metabolic pathway

Agonist vs. Antagonist

• Agonist: Binds to a receptor and initiates the expected response
• Antagonist: Binds to a receptor site, blocking or preventing the expected response
• Agonist-antagonist: Can initiate or block the expected response

Responses to Drug Administration

• Allergic reaction
• Idiosyncrasy
• Tolerance
• Cross tolerance
• Tachyphylaxis
• Cumulative effect
• Drug dependence
• Drug interaction
• Drug antagonism
• Summation
• Synergism
• Potentiation
• Interference

Drug-Response Relationship

• Onset of Action: The time it takes for a drug to reach its minimum effective concentration
• Duration of Action: The length of time a drug remains at an effective level
• Termination of Action: When drug levels drop below the minimum effective concentration until its eliminated from the body
• Therapeutic Index: Indicates that the medication is effective, without unaccepted adverse events
• Half-life: The time needed for the body to eliminate one-half of the drug

Factors Altering Drug Response

• Age
• Body mass
• Sex
• Environmental
• Time of administration
• Pathology
• Genetics
• Psychology

Medication Administration

• Right Patient
• Right Medication
• Right Dosage
• Right Route
• Right Time
• Right Documentation
• Right Client Education
• Right to Refuse
• Right Assessment
• Right Evaluation

Medication Legislation

• Pure Food and Drug Act of 1906
• Federal Food, Drug and Cosmetic Act
• Harrison Narcotic Act of 1914

DEA

• Drug Enforcement Agency

U.S. DEA Drug Scheduling

• Schedule I*
• Definition: Drugs with no currently accepted medical use and a high potential for abuse
• Examples: Cannabis, Heroin, and LSD
• Schedule II*
  • Definition: Drugs with a high potential for abuse that may lead to severe psychological or physical dependence Examples: Vicodin, Cocaine, and Methamphetamine
• Schedule III*
  • Definition: Drugs with a moderate to low potential for physical and psychological dependence. Less abuse potential than Schedules I and II, but more than Schedule IV
  • Examples: Ketamine, anabolic steroids, and testosterone
• Schedule IV*
  • Definition: Drugs with a low potential for abuse and low risk of dependence
  • Examples: Xanax, Ambient, and Valium
• Schedule V*
  • Definition: Drugs with lower potential for abuse than Schedule IV, often used for antidiarrheal, antitussive, and analgesic purposes
  • Examples: Robitussin A-C, Motofan, and Lyrica

Development of Pharmaceuticals

• Development of pharmaceuticals has involved apothecaries, physicians, organization, modern discoveries in medicine, and legislation approval processes

Sources of Drugs

• Plants
• Animals
• Minerals
• Synthetic/semi-synthetic
• Extracts
• Alkaloids
• Genetic

FDA Drug Approval Process

• Pre-Clinical
• Drug Developed
• Animals Tested
• Investigational New Drug (IND) Application
• Clinical - Phase 1 - Phase 2 - Phase 3
• New Drug Application (NDA) Review
• Review Meeting
• New Drug Application (NDA)
• Application Reviewed
• Facility Inspection
• Drug Labeling
• Drug Approval
• Post-Marketing
  • Phase 4

Overview of pharmacokinetics, including absorption, distribution, biotransformation, and elimination. Review routes of drug administration (IV, IO, ET, etc.) and their peak effects. Also diffusion, where molecules move from high to low concentration, and osmosis, where solvent moves across a semipermeable membrane.