Pharmacokinetics Flashcards
What does Pharmacokinetics include? (3)
HINT- ADME
Absorption
Distribution
Elimination via Metabolism or Excretion
Why do drugs need to be in an aqueous solution?
water is a universal solvent
distribution around body, interact with target molecule, enable passage to organs
Why is it useful for drugs to have some lipid solubility?
to distribute in fatty tissue & to cross cell membranes
How do drugs pass into/ from circulation?
cross via vascular endothelium through gaps between cells
What three factors effect drug movement and how?
- molecular weight- high molecular weight will remain at sight of administration for longer
- lipid solubility- to pass through membranes
- chemical nature- if it is neutral, acid or base (variation of ionisation)
Why does the degree of ionisation effect drug movement? Give examples.
Weak acids/ weak bases- partially ionised, readily cross membranes
strongly acidic or basic- 100% ionised and do not cross
The rate/ extent of drug absorption is affected by what?
- properties of the drug
- pH at site of absorption/ ionisation, area of absorption surface, local blood flow (These are all physiological variables)
- the formulation of the drug
Does the small intestine have a higher or lower absorption compared to the stomach and why?
Higher !
Larger surface area
What does first pass metabolism mean?
where a drug is extensively metabolised in the wall of the GIT, liver etc. before it reaches systemic circulation
What is bioavailability?
the fraction of the dose of the drug that reaches the systemic circulation in an active form
How is the route of a drug determined? Give an example.
by property of drug & therapeutic objective
e.g. some you can’t give orally due to inability to survive in gastric acid of stomach
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