drug absorption and distribution Flashcards
3 factors to consider in drug absorbtion
- drug properties
- patient factors
- possible routes of admin
4 mechanisms of drug absorption (cellular)
- passive diffusion
- facilitated diffusion
- active transport
- phagocytosis
3 properties of drugs that affect absorption
- chem structure size etc.
- lipid and water solubility
- ionization
what is usual molecualr weight of drugs
250-450 Da
at what size can a lipid soluble drug diffuse across membrane
1000Da
what is partition coefficient
[drug in membrane]/[drug in buffer]
what does higher partition coeff. mean
more lipid soluble
what increase and decrease PC
incr- hydrophobic groups (benzene, CH3)
dec. - hydrophilic groups - OH, COOH,
what is the effect of drug ionization
uncharged form is generally easier to cross membrane
** what happens with higher Ka in acid and basic drug - when increase pH over pKa
acid - more ions
basic - less ions
what are drug transporters
proteins responsible for moving drugs into and out of cells
most common locations of transporters
apical layer of hepatocytes, enterocytes, tubular cells
2 main classes of drug tranporters
- uptake transporters
2. efflux transporters
why are transporters relevant
- also affects distribution and elimination
2. need to know if drug is a substrate, inhibitor, or inducer of transport
what is volume of distribution
volume of total body fluid that is absorbing the drug