Drug Distribution, Metabolism & Elimination Flashcards
define drug distribution
is the reversible transfer of drug to
and from the site of measurement
what is whole blood
blood outside the body with anticoagulant
what is serum
blood in a collecting cute without anticoagulant (allowed to clot for 20 mins)
what is the role of plasma protein binding
it removes the drug from free solution
- meaning the drug is no longer free to diffuse into the surrounding tissue
how does plasma protein binding aid absorption and transport of the drug
By keeping lipophilic drugs in solution
what is bioavailability
the extent to which a drug can overcome the barriers of absorption (including first pass metabolism) and enter the systematic circulation
what is the blood brain barrier (BBB)
tight junctions between endothelial cells and glial limitans, restrict access to cerebrospinal
what drugs can pass through the BBB
only lipid soluble drugs
water soluble drugs diffuse slower across the BBB than any other membrane barriers
what illness compromises BBB integrity
meningitis
how do drugs access a foetus
enters the maternal blood pool and diffuse into foetal capillaries
what is drug distribution to foetus’s limited by
lipid solubility and size
what does accumulation of drugs depend on
blood flow into the tissue
if free concentration is high
it shows that the dug is still in the blood not the tissue, and isn’t being properly distributed
what carries drugs through the bloodstream
albumin
what is an example of a Highly-perfused lean tissue group
- blood cells
- heart
- lungs
- liver
-kidney
what is an example of a poorly-perfused lean tissue group
- muscle
-skin
what is an example of a fat group
- adipose tissue
- bone marrow
what is an example of a negligible -perfusion group
- teeth
- hair
- bone
- tendons
- cartilage
are Drugs with a high lipid/water partition coefficient fat soluble
yes very
where do drugs with a high lipid/water partition coefficient tend to accumulate
in lipid or adipose (fat) tissue
what is thiopental
is an induction anaesthetic, it is highly lipid soluble, delivered by
rapid iv infusion
what is volume of distribution
the theoretical volume of plasma that would accommodate total drug amount at the measured plasma concentration
how do you work out Vd (volume of distribution)
Vd = amount in body / concentration in blood
