Drug distribution Flashcards
drug distribution
the Reversible Transfer of a Drug between the Blood and the Extra Vascular Fluids and Tissues of the body
factors that affects the amount of bound drug to plasma proteins
- renal failure (less binding therefore increased distribution)
- hypoalbuminaemia (less binding increases distribution)
- pregnancy (decreased binding increased distribution)
- other drugs
- saturability of binding
Apparent Volume Of Distribution (Vd)
Fluid volume that would be required to contain the amount of drug present in the body at the same concentration as in the plasma
the greater the Vd the…
greater the ability of the drug to diffuse into and through membranes
Vd of highly protein bound drug
3L
clearance
the theoretical volume from which a drug is completely removed over a period of time. it is a measure of elimination
what is clearance dependent on?
- conc.
- urine flow rate
- metabolism
- biliary excretion
biliary excretion
Irreversible transfer of drug or drug metabolites from the plasma to the bile through the hepatocytes
half life ( t1/2)
time taken for the drug concentration to drop by a half of the current value
effect of prolongation of half life
increase in toxicity, due to reduction in clearance and large volume distribution.
chronic administration
used to reach a therapeutic range, this may take 4 or 5 doses/ half-lifes
how does half life affect time to stabalisation
the longer the half life the longer the time to stabalisation and the therapeutic range
2 parts of drug elimination
drug metabolism
drug excretion
three principal mechanisms for excretion form kidneys
- glomerular filtration
- passive tubular absorption
- active tubular absorption
glomerular filtration
filters out unbound drug
