Pharmacology

• Pharmacokinetics


  The study of the effect the body has on drugs
• Pharmacodynamics


  The study of the effects of drugs on the body
• ADME


  • Absorption
  • Distribution
  • Metabolism
  • Excretion
• ADME are the four elements to consider when talking about the pharmacokinetics of a drug
• The concentration of a drug in the body increases when it enters the body faster than it is being removed
• Cmax


  The highest concentration of drug in the body
• Tmax


  The time at which the maximum concentration occurs
• Half Life

  The time it takes to remove half of the current concentration of drug from the body
• Volume of distribution (Vd)

  Total amount of drug in body divided by concentration in plasma, indicates how much drug is needed to achieve a certain plasma concentration
• Drug metabolism


  The process by which drugs are broken down and transformed in the body
• Drug metabolism


  • Often takes place in the liver
  • Can also take place in the lungs or the gut
• First pass metabolism


  The phenomenon where drugs given orally may be metabolized by the liver before they reach the systemic circulation
• Drugs with significant first pass metabolism

  • Morphine
• Cytochrome P450 enzymes (CYP)

  Enzymes that metabolize drugs through processes like oxidation, hydrolysis and hydroxylation
• Prodrug


  A drug that needs to be metabolized to become active
• Drug metabolites can be easily excreted by the kidneys after phase 1 and phase 2 metabolism
• Drug interactions can occur when two drugs are administered together and affect their absorption, distribution, metabolism, or excretion.
• The liver is the primary site of drug metabolism, with enzymes such as cytochrome P450 (CYP) playing a major role.
• Excretion


  The irreversible removal of drugs from the body
• Ways the body excretes drugs

  • Hepato-biliary system
  • Kidneys
• Hepato-biliary system


  The liver excretes a drug or drug metabolites into the bile which is then excreted in the feces
• Most drugs are primarily excreted by the kidneys
• Kidney excretion process


  1. Drug filtered into nephron

  2. Flows through nephron into collecting ducts

  3. Excreted in urine
• Clearance


  The concentration of a drug in the urine times the rate at which the urine is being produced, divided by the concentration of drug in the plasma
• Clearance is a volume of plasma per unit time that is cleared of the drug
• Clearance indicates how quickly a drug can be eliminated from the plasma
• Factors affecting clearance


  • Plasma drug concentration (related to dose)
  • Urine volume (related to glomerular filtration rate)
• Drug reabsorption in nephron


  Decreases urine concentration and clearance
• Drug secretion into nephron

  Increases urine concentration and clearance
• First-order kinetics


  Higher plasma concentration leads to faster elimination, with a constant half-life
• Zero-order kinetics


  Elimination rate is independent of plasma concentration, with a variable half-life
• Once enzyme is no longer saturated, elimination follows first-order kinetics
• Pharmacotherapeutics


  The study of the therapeutic uses and effects on drugs
• Epidemiology


  The study of the effect of drugs on populations
• Pharmacoeconomics


  The study of the cost-effectiveness of drug treatments
• Bioavailability 


  How much of the drug is available for use?
• What is the bioavailability for IV drugs?

  100%
• What is the bioavailability for oral drugs?

  15%
• Nephrotoxic


  Medicines that have a toxic effect on the kidneys
• Label the neuron

  A) Dendrite

  B) Nucleus

  C) Cell body

  D) Axon Hillock

  E) Mylein Sheath

  F) Node of Ranvier

  G) Schwann Cell

  H) Axon Terminal