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Sem. B - Pharmacology > Pharmacokinetics > Flashcards

Flashcards in Pharmacokinetics Deck (6)
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1

Definition

Study of how drugs enter the body, reach their site of action and are elimated by the body

 

ie. What the body does to the drug!

2

Liberation

  • Only applies to oral drugs
  • Process by which a drug is released from its delivery device during digestion
    • tablet, capsule, etc
  • Rate of liberation is determined by its composition
    • powder vs tablet

3

Absorption

  • How a drug enters the bloodstream
  • Depends on:
    • route of entry
    • character of drug
  • Factors affecting absorption:
    • pH of the drug
    • Lipid/water soluble
    • Surface area of the drug
    • Surface area of the absorping environment
    • Rate of blood flow
      • hypothermia
      • shock
    • Drug concentration
    • Design of the drug
    • Delivery route

4

Distribution

  • The distribution of a drug around the body's bloodstream and cells
  • Dependant on chemical properties of the drug and its ability to:
    • cross cell membranes
      • passive diffusion
      • diffusion through aqueous channel
      • facilitated diffusion with carrier proteins
      • active transport against concentration gradient with input of energy
    • penetrate capillaries
    • cross blood-brain barriers
    • cross the placenta
  • Factors affecting distribution:
    • protein & tissue binding
    • perfusion status
    • vascular supply to the target tissue
    • blood pH
    • presence of other protein binding drugs
    • CNS blood brain barriers
    • placental barrier
    • competing tissues

5

Metabolism

  • How a drug is changed by the body
  • Complex liver enzyme system converts lipid soluble drugs to water soluble metabolites
  • easier to eliminate
  • Drugs absorped via the GI tract enter the liver before entering the general circulation which can metabolize/inactivate drugs before they distribution throughout the body
    • good if drugs are harmful/potent
    • prevents drugs such as GTN being given orally

6

Elimination

  • How drugs are removed from the body after metabolism:
    • kidneys - urine
    • bile
    • expired air
    • sweat
    • tears
    • faeces
  • Half-life is the amount of time required for elimination processes to reduce drug serum concentration by half