Pharmacology - Pharmacokinetic

  • Created by: Sophie
  • Created on: 16-01-13 15:44
View mindmap
  • Pharmacokinetics
    • Drug Elimination
      • The irreversible loss of drug from the body
      • Occurs by 2 processes; metabolism + excretion
      • Metabolism consists of anabolism + catabolism
      • Most drugs leave the body via the kidneys, lungs or hepatobiliarysystem
    • Drug Metabolism
      • Enzymatic modification of drug molecule
        • New molecules may be:
          • Active; change in pharmacology, toxicology, duration
          • Inactive
      • Involves 2 kinds of reaction; Phase 1 and Phase 2
        • Phase 1 reactions are catabolic
        • Phase 2 reactions are anabolic/ synthetic
    • Excretion
      • Elimination of drug and metabolites from the body
      • Excretion through kidneys, GI tract, lungs, sweat, tears, mil
      • Renal excretion:
        • 1. Glomerular Filtration
          • Allow molecules of <20000 to pass
          • Most drugs are potentially filterable
          • Filtratability affected by binding of drug to plasma proteins; only unbound are filtratable
        • 2. Tubular Secretion
          • Renal tubules contain transporter proteins that pump drugs across membranes
          • Many drugs are pumped across membrane by same transporter
            • Gives potential for drug interactions due to competition
          • Active transport will pump drugs that are bound to plasma proteins
            • Binding of drugs to plasma proteins is reversible
        • 3. Diffusion across Renal Tubule
          • Glomerular filtrate is concentrated in renal tubule
          • Reabsorption of water
            • Increase in drug
              • Non-polar drug = drug reabsorption by increasing conc. gradient
                • Polar drug = little reabsorption, drug is excreted in urine eg. penicillin
          • Ion trapping in Renal Tubule
            • Ionisation of weak acids + weak ases changes with pH
            • Degree of ionisation can change the rate of drug excretion
              • Alkaline urine increases excretion of weak acids
                • Acidic urine increases excretion of weak bases
      • Biliary Excretion
        • Liver cells transport drugs from plasma into bile
          • Bile is excreted into intestine
          • Involves active transport
            • Uncharged drug eg. digoxin
              • Unconjugated drug eg. morphine as glucuronide
    • Quantitative
      • Why study pharmacokinetics?
        • To determine dose and frequency of admin.
        • To explain diff. in response to a drug
      • To study:
        • 1. Inject a small dose
        • 2. Measure disappearancefrom plasma at various times
        • 3. Use resulting data to determine Vd and eliminations rate
          • Kel = Kexc + Kmet


Rose Westhorpe



Similar Biology resources:

See all Biology resources »