12 OTC Analgesics

Public Lecture Overview

  • Title: The Art & Science of Brain Rhythms

  • Date & Time: February 6, 2025, at 6:00 PM

  • Location: Myer-Horowitz Theatre

  • Presenters:

    • Clayton Dickson (Scientist)

    • Kyle Mathewson (Scientist)

    • Janette Mailo (Neurologist)

    • Gary James Joynes (Sound Artist)

  • Host: Anna Taylor

  • Organized by: Neuroscience and Mental Health Institute, University of Alberta

  • Event Details:

    • Interactive discussion on how sound rhythms affect the mind and brain function.

    • Free tickets available.

Over-The-Counter (OTC) Drugs Overview

  • Focus of Study: Analgesics

  • Course Code: PMCOL 200

  • Instructor: Dr. Anna Taylor

Pain Management Content

Key Topics Covered

  • Review of peripheral pain circuitry.

  • Types of pain relief drugs:

    • NSAIDs: Treat inflammation and fever.

    • Topical Anesthetics: Block sensation.

    • Capsaicin Cream: Blocks pain.

Learning Objectives

  • Describe pathways of pain transduction.

  • Identify OTC drugs for pain and explain their mechanisms.

Peripheral Pain Circuitry

Neuron Types

  • Primary Afferents:

    • Detect sensory info from the periphery (skin, GI tract).

    • Transmit information to spinal cord.

    • Synapse with secondary afferents to relay data to the brain.

  • Motor Efferents:

    • Deliver motor commands from the brain to muscles.

Pain Detection Mechanism

  • Nociceptors:

    • Class of primary afferents that detect pain stimuli (thermal, mechanical, chemical, electrical).

    • Polymodal Nociceptors:

      • Detect multiple types of painful stimuli, densely innervate all body surfaces.

Pain Importance

  • Pain serves as a critical warning system for injury or potential harm.

Specific Pain Stimulus Detection

Receptors and Signaling

  • TRP Channels:

    • Temperature-sensitive, ligand-gated ion channels.

    • Specific types:

      • TRPM8: Activates below 10°C (cold).

      • TRPV1: Activates above 43°C (hot).

  • Activation by ligands:

    • TRPV1 → Capsaicin.

    • TRPM8 → Menthol.

Inflammatory Response

  • Receptors responsive to inflammatory molecules (bradykinin, cytokines, prostaglandins).

  • Inflammation triggered following tissue injury or infection leads to pain signaling.

Inflammation and Pain Modulation

Arachidonic Acid Pathway

  • Arachidonic acid derived from phospholipids in cell membranes.

  • Metabolized by enzymes COX1 and COX2 into prostaglandins and thromboxanes, influencing inflammation and pain responses.

Key Molecules in Inflammation

  • Prostaglandin E2 (PGE2):

    • Potent vasodilator, induces fever, attracts immune cells.

  • Thromboxane A2:

    • Promotes platelet aggregation and vasoconstriction.

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

Mechanism of Action

  • NSAIDs block COX1 and COX2, decreasing prostaglandin production to reduce inflammation and pain.

  • Aspirin:

    • Irreversible inhibitor; long half-life due to binding to catalytic sites.

Side Effects

  • Gastric Toxicity:

    • Common with chronic NSAID use due to COX1 inhibition, can cause ulcers and bleeding.

    • Ketorolac: Highly effective but has associated risks.

COX2 Specific Inhibitors

  • Developed to reduce gastric toxicity, but may increase cardiovascular risk.

Acetaminophen

Profile and Mechanism

  • Used since the 1800s; identified as a weak COX1 and COX2 inhibitor.

  • Recent findings (2002) suggest inhibition of a third isoform (COX3) concentrated in the cerebral cortex.

Safety and Risks

  • Minimal toxicity at therapeutic doses; overdose can lead to severe liver damage.

Local Anesthetics

History and Development

  • Cocaine was the first local anesthetic identified; later substituted by synthetic alternatives due to addiction risks.

    • Examples: Procain, Lidocaine, Bupivicaine.

Mechanism of Action

  • Local anesthetics block sodium channels crucial for action potential propagation, potentially leading to motor paralysis.

  • Effective in blocking active nociceptors preferentially during pain.

Capsaicin and Pain Management

Capsaicin Cream Mechanism

  • Acts as a TRPV1 receptor agonist leading to initial burning sensation.

  • Continuous use induces desensitization of TRPV1+ nociceptors, leading to pain relief.

Sensory Pathway Overview

  • Review of Pain Modulation:

    • Various methodologies including NSAIDs, acetaminophen, topical anesthetics, and capsaicin for managing pain.

  • Pain as the primary reason for medical consultations, with ongoing research into mechanisms, especially for acetaminophen.