StudyLoop

Pharmacokinetics: Absorption, Distribution, Protein Binding, Metabolism (including first-pass and Phase I and II)

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  • Absorption
    • Affected by weight, solubility, and other factors: Influences how a drug enters the bloodstream.
    • GI factors like food can change absorption: Presence of food can alter drug absorption rates.
  • Distribution
    • Membrane permeability (e.g., blood-brain barrier): Determines which drugs can enter the CNS.
    • Plasma protein binding
      • If not bound, higher levels in blood and tissues: Only unbound drugs are active.
    • Storage
      • Lipophilic drugs accumulate in fats, calcium in teeth: Affects drug storage and release.
  • Metabolism
    • Phase I (non-synthetic): drugs are oxidized or reduced to more polar forms
    • Phase II (synthetic): polar groups like glutathione are conjugated to the drug
    • Cytochrome P450 metabolism
      • Mixed function, catalyzes the metabolism of many drugs, delays metabolism or extends life of competing drugs: Plays a crucial role in drug interactions.

Excretion: Renal, Biliary, Other (e.g., for volatile drugs)

  • Renal
    • Organic anion transport: HCTZ, furosemide, PCN G, salicylates: Mechanism for drug excretion through kidneys.
  • Biliary excretion
    • Drugs excreted into bile and eliminated in feces: Alternative route of excretion.
  • Other
    • Volatile drugs excreted through lungs: e.g., anesthetic gase