Drug Absorption Flashcards
What is definition of absorption?
Process by which unchanged drug enters circulation
What is definition of distribution?
Dispersion of drug among fluids + tissues of body
What is definition of metabolism?
Transformation of drug into daughter compounds
What is definition of excretion?
Removal of drugs/metabolites from body
What are the routes of administration of drugs?
Intramuscular, subcutaneous + intravenous
Absorption can occur by…..
Active transport through cells- very few medicines
Facilitated diffusion through cells- few medicines
Passive diffusion- most medicines
What is Fick’s law?
Rate of diffusion= surface area x conc difference x permeability
What are the factors affecting permeability?
Molecular size, lipid solubility, presence of charged or ionisable groups
What is key determinant of permeability?
Lipid solubility/ ionisation
What are factors that increase rate of diffusion?
Increase in SA, conc difference + permeability
Most drugs are ……
Weak acids or bases thus ionisable
Extent of ionisation depend on …..
pH of environment
Acid-base dissociation constant of drug
To diffuse across the cell membrane, medicines must be ……
Uncharged, non-ionisable, lipophilic
What does Henderson Hasselbalch predict?
It predicts extent of ionisation
What is Lipinski rules?
A rule based approach to ADME optimisation
An orally active drug has no more than one violation of following
Molecular weight <500
No more than 5 H bond donors
No more than 10 H bond acceptors
Log p<5 (partition coefficient)
