NUERO 2/24

Overview of Drug Mechanics
  • Introduction to drug discussion
    • Discussion of drugs generally, then specifics
    • Topics include tolerance and addiction
  • Reminder about class schedule
    • No class on Wednesday due to a meeting
    • Quiz due by Wednesday, format same as previous, multiple attempts allowed
Key Terms
  • Ligand: Any chemical that interacts with a receptor, having an affinity for it.
  • Blood-Brain Barrier: A protective barrier that prevents potentially harmful substances from entering the central nervous system (CNS) by maintaining tighter junctions in capillaries.
    • Created by glial cells, especially astrocytes that wrap around blood vessels in the CNS.
Ligands and Receptors
  • Binding Affinity: The degree to which a ligand is attracted to a receptor. This affects how drugs interact with neurotransmitter sites.
  • Efficacy: The ability of a drug to produce a maximal response in a neuron.
    • Agonist drugs enhance neurotransmitter activity (high efficacy).
    • Antagonist drugs reduce neurotransmitter effects (low efficacy).
    • Partial Agonists: Produce moderate effects, useful for balancing neurotransmitter action.
Drug Effects and Dosage
  • Drug response can significantly change with dosage:
    • Higher doses may activate multiple receptor types leading to stronger effects.
    • Dose-Response Curve: A visual representation showing the relationship between drug dose and effect, usually wavy rather than linear.
  • Effective Dose (ED): Usually set at the level to achieve 50% effect, commonly used to determine prescription dosages.
  • Lethal Dose (LD): The dosage at which drugs can cause death, important for assessing safety.
    • Therapeutic Index: The difference between effective dose and lethal dose; a wider index is safer (e.g., lorazepam vs. phenobarbital).
Pharmacokinetics
  • Pharmacokinetics: The study of how drugs move through the body:
    • Routes of Administration:
    • Oral: Drug is ingested and absorbed in the digestive system.
    • Injection: Can be intravenous (directly into blood), intramuscular (into muscle), or subcutaneous (under the skin).
    • Transdermal: Through the skin via patches.
    • Mucous Membranes: Absorbed from under the tongue or through the nasal cavity.
    • Intrathecal: Directly into spinal fluid method, used sparingly.
    • Bioavailability: The proportion of the drug that enters circulation and has active effects.
  • Metabolism: How drugs are broken down (often in the liver), affecting bioavailability and duration of effect.
    • Active Metabolites: Some drugs are metabolized into other compounds that have effects on the body (e.g., codeine into morphine).
Drug Interactions and Tolerance
  • Tolerance describes the body's decreasing response to a substance over time:
    • Metabolic Tolerance: Increased breakdown of the drug by the liver, reducing efficacy.
    • Functional Tolerance: Changes in the number or sensitivity of receptors.
    • Downregulation upon agonist use and upregulation upon antagonist use.
    • Learned Tolerance: Classical conditioning where the body anticipates drug effects based on context, affecting real-time responses and increasing overdose risks in novel environments.
    • Cross Tolerance: Tolerance to one drug may carry over to others within the same class, complicating treatment adjustments.