Absorption and Distribution of Drugs Flashcards
What does absorption mean
From site of administration to plasma
What does distribution mean
Distribution of absorbed drug around body
How do drugs pass through thin layers
Passive diffusion - through cells or intracellular pores
Facilitated diffusion
Active transport
What is ion trapping
Drugs tend to accumulate in area where ionisation is favoured
What happens to weak acidic drugs
Well absorbed from acidic environments but accumulate in basic environments
Which is lipid soluble: ionised or unionised
Only unionised
What is bioavailability
Fraction of total dose administered that reaches plasma
What is bioequivalence
Absorbed + eliminated at same rate
What are the factors affecting absorption from GI
Lipid solubility Time available for reabsorption Concentration of drug Blood flow Stability of drug - acid/alkali? First pass metabolism in gut wall Interaction with food
What are the factors affecting transdermal absorption
Lipid solubility
Skin thickness
Hydration - Increase hydration = increase absorption
Blood flow
Formulation - Active drug + different chemicals = final medicinal product
How can we influence the absorption of drugs
Particle Size
Enteric coated tablets
Slow release preparations
Implantable preparation
What influences distribution
Competition between drugs - aspirin displaces warfarin (protein binding)
Apparent volume of distribution: volume of fluid required to dilute absorbed dose to concentration found in plasma
Why is our body a dynamic environment
Bulk flow = protein with sorting signal will travel to/from specific location
Nature of absorptive surface
