Medicinal Chemistry: Painkillers, Infections, and Chemotherapy Study Guide PowerPoint

Learning Objectives for Medicinal Chemistry

  • Define Painkillers: Understand the classification and scope of drugs specifically used for pain relief.
  • Mechanisms of Action: Explain the physical and chemical processes by which painkillers function within the human body.
  • Viral vs. Bacterial Infections: Describe the structural and biological differences between these two types of pathogens.
  • Other Sources of Infection: Describe fungi, protozoa, helminths, and prions as agents of disease.
  • Vaccinations: Summarize the immune response mechanisms triggered by vaccines.
  • Chemotherapy: Define chemotherapy and explain the techniques and mechanisms used to stop or slow cancerous growth.
  • Placebo Effect: Describe why the placebo effect is considered a valid form of clinical treatment.

Fundamental Definitions

  • Drugs: Any chemical substance which results in a physiochemical effect once it has entered the body.
  • Painkiller: Specifically defined as drugs which provide pain relief.

Classifications and Sources of Drugs

Natural Drugs

Drugs derived directly from biological organisms without significant chemical modification.

  • Microorganisms: Species of microorganisms serve as the source for Penicillin, a foundational antibiotic.
  • Plant Sources:
    • Quinine: Extracted from tree bark; specifically used to treat malaria.
    • Morphine: Extracted from the opium poppy (PapaversomniferumPapaver somniferum). Associated with the work of Hermann Adolf Köhler (1834 - 1879).

Semi-Synthetic Drugs

These are derivatives of compounds extracted from plants or animals, modified in a laboratory.

  • Salicylic Acid: Found in willow bark; it serves as the starting material to synthesize Aspirin.
  • Codeine: Produced by replacing one functional group on the morphine molecule.
  • Opioid Derivatives: Including Hydromorphone, Hydrocodone, Oxycodone, and Buprenorphine.

Synthetic Drugs

Completely man-made compounds synthesized in a laboratory setting.

  • Methadone: Used primarily to treat heroin addiction and withdrawal symptoms.
  • Fentanyl: A powerful synthetic drug used for significant pain relief.

General Drug Functions

  • Analgesic: Provides pain relief.
  • Antipyretic: Reduces fever.
  • Anti-inflammatory: Reduces inflammation.
  • Note: Many painkillers are multi-functional, providing a combination of these therapeutic effects.

Non-Narcotic Painkillers: Acetaminophen and NSAIDs

Acetaminophen (Paracetamol)

  • Functions: Primarily an analgesic (pain relief) and antipyretic (fever reduction).
  • Mechanism: Reduces the production of pain-signaling molecules specifically in the brain.
  • Side Effects: Potential for severe liver and kidney damage; dangerous when interacting with alcohol.
  • Common Brand: Tylenol, Panadol.

NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)

  • Functions: Analgesic, antipyretic, and anti-inflammatory.
  • Mechanism: Prevents the formation of molecules that cause inflammation and fever.
    • Non-selective: Works throughout the entire body.
    • Selective: Targets specific enzymes, often sparing those that control the stomach lining.
  • Side Effects: Excessive bleeding and stomach pain/damage.
  • Common Brands and Compounds:
    • Aspirin: A salicylate drug; inhibits cyclo-oxygenase enzymes (COX), preventing prostaglandin formation. Often prescribed for blood clot prevention.
    • Ibuprofen: A phenylpropanoic acid; trade names include Advil, Nurofen, Motrin, and Brufen. It inhibits COX enzymes.
    • Naproxen: Long-acting NSAID.
    • Celebrex: A selective NSAID that targets specific enzymes to reduce stomach irritation.
  • Combination Drugs:
    • Excedrin: Acetaminophen + Aspirin + Caffeine.
    • Anacin: Aspirin + Caffeine.

Opioids and Narcotics

General Characteristics

  • Used for general anesthesia and severe pain relief.
  • High potential for addiction.
  • Critical Risk: At high doses, breathing may be inhibited (respiratory depression).

Potency Comparison

Potency is measured relative to Morphine (assigned a baseline value of 1) for oral administration. Values are general approximations:

  • Tramadol: 0.10.1 (Synthetic opioid; inhibits noradrenaline and serotonin reuptake).
  • Codeine: 0.10.1 (Naturally occurring; most widely used opiate in the world; often found in Co-codamol with paracetamol).
  • Morphine: 11 (Naturally occurring; first plant alkaloid isolated; brands: MS Contin, Oramorph, Sevredol).
  • Hydrocodone: 11 (Semi-synthetic; ~99% of world supply consumed in the USA; brand: Vicodin when mixed with paracetamol).
  • Oxycodone: 1.51.5 (Semi-synthetic; brand: OxyContin, Roxicodone, Oxecta).
  • Methadone: 55 (Synthetic; brands: Methadose, Dolophine).
  • Hydromorphone: 4−74 - 7 (Semi-synthetic; used intravenously in hospitals; brands: Palladone, Dilaudid).
  • Buprenorphine: 4040 (Semi-synthetic; potent local anesthetic properties; used to treat opioid dependence; brands: Suboxone, Subutex).
  • Fentanyl: 80−10080 - 100 (Synthetic; used during surgical procedures; brands: Actiq, Durogesic, Abstral).

Consumer Precautions

  • Active Ingredients: Users must identify the specific active ingredients in all medications.
  • Redundancy: Avoid taking multiple medications at the same time to prevent an inadvertent increase in dose (double-dosing on the same active ingredient).
  • Medical Consultation: Always consult with a physician to avoid drug-drug interactions and medical complications.

Infectious Agents and Diseases

Viruses

  • Structure: Composed of nucleic acids (DNA or RNA) enclosed in a protein shell, sometimes with a lipid envelope.
  • Diseases: Common cold, Measles, Influenza, Chicken pox.

Bacteria

  • Structure: Single-celled organisms, significantly larger than viruses.
  • Characteristics: Capable of genetic evolution (leading to resistance).
  • Diseases: Strep throat, Tuberculosis (TB), staph skin infections, urinary tract infections (UTI), and bloodstream infections.

Fungi

  • Transmission: Infections start once spores land on the skin or are inhaled.
  • Diseases: Athlete’s foot, Ringworm.

Protozoa

  • Structure: Single-celled organisms.
  • Transmission: Often ingested or injected (e.g., via a mosquito bite).
  • Diseases: Malaria, Dysentery.

Helminths

  • Nature: Tiny parasitic worms.
  • Diseases:
    • Schistosomiasis: Spread to humans via snails.
    • Worm types: Tapeworms, flukes, and roundworms.

Prions

  • Nature: Protein packets (infectious proteins).
  • Characteristics: Highly resistant to standard bacterial killing methods.
  • Diseases: Mad cow disease.

Curing and Treating Disease

  • Antibacterial Drugs: Designed to prevent the growth and biological function of specific bacteria.
  • Antiviral Drugs: Designed to prevent the reproduction of active viruses within the body.
  • Influenza (The Flu):
    • Spread via ingestion or inhalation.
    • The Flu Vaccine: Administered annually; formulated to be insensitive to specific mutations in the virus cell.
    • Note: Antibacterials are completely ineffective against the flu virus.
  • Vaccines: Work by "decoding" or preparing the immune system to recognize pathogens.

Chemotherapy

Definition

The use of drugs to stop or slow the growth of cancerous cells.

Types of Chemotherapy Agents

  • Alkylating Agents: Directly damage DNA to prevent cancer cells from reproducing.
  • Plant Alkaloids: Derived from plants; interfere with cell division.
  • Anti-tumor Antibiotics: Drugs that interfere with DNA inside cancer cells.
  • Anti-metabolites: Molecules that masquerade as nutrients for the cell, effectively "starving" or blocking the growth machinery of the cancer cell.

The Placebo Effect

  • Definition: A phenomenon where a patient experiences a real improvement in their condition after receiving a "dummy" treatment (one with no active medicinal ingredient).
  • Mechanism: Rooted in the science of how mindset transforms the human biological experience. It is explored as a legitimate aspect of medical treatment and clinical study controls.