Chapter 1

• Drug


  Any substance that alters the physiology of the body, but is not a food or nutrient
• Names of drugs


  • Chemical name
  • Generic name
  • Trade name
• Drug dosages


  • Metric and effectiveness (X mg/kg)
  • Dose response curve

  
• Median effective dose (ED50)

  Dose at which 50% effected
• Median lethal dose (LD50)

  Dose at which 50% died
• Potency


  Difference in ED50
• Effectiveness


  Difference in maximum effect
• Drug interactions


  1. Antagonism

  2. Additive effect

  3. Superadditive effect or potentiation
• Pharmacokinetics


  How drugs move about the body
• Routes of drug administration

  • Parenteral
  • Inhalation
  • Oral
  • Transdermal
• Parenteral administration


  • Requires vehicle solution
  • Subcutaneous (sc.)
  • Intramuscular (i.m.)
  • Intraperitoneal (i.p.)
  • Intravenous (i.v.)
• Inhalation


  • Inhaled into moist surface of lungs
  • Pores in capillary walls to circulating blood
  • Burning plants carry active ingredient in smoke
  • Powdered drugs dissolve into moist mucous membrane
• Oral administration


  • Intestines of digestive system
  • Lipid bilayer with no pores - lipid-soluble to pass, if charged (ion) can't pass
  • Ionization determined by drug, environment pH, and pKa
• pH of a solution is a measure of hydrogen ion (H+) concentration
• Ion-trapping occurs with oral administration
• Transdermal administration


  • Epidermis is impermeable to water
  • Used for drugs like nicotine and scopolamine
• Factors affecting drug distribution

  • Lipid solubility
  • Capillary pores
  • Blood-brain barrier
  • Passive and active transport
  • Protein-binding
  • Placental barrier
• Excretion and metabolism


  • Liver and kidneys
  • Nephrons in kidneys
  • Liver enzymes change drug structure (metabolism)
• Half-life


  Time to reduce current concentration to half
• Factors that alter drug metabolism

  • Heavy alcohol drinking increases enzyme induction
  • Enzyme depression
  • Disulfiram competes with acetylaldehyde
• Age and drug metabolism


  • Enzyme systems take time to develop after birth
  • Liver functioning declines with age