distribution Flashcards
what is the order of pharmacokinetics?
absorption, distribution, metabolism (elimination)and excretion (elimination)
what is distribution
process of reversible transfer of drug from bloodstream to other parts of the body
what factors affect rate and extent of distribution?
permeability of tissue membranes to the drug
ion trapping
pKa
how well perfused the organs/tissues are to the drug
binding of the drug to the plasma proteins/tissue components
p-glycoproteins
which patient characteristics affect drug distribution?
age
gender
weight loss-obesity
ethnicity
health status
pregnancy
oedema-dehydration
how does body water change with age?
it decreases with age (from premature to elderly)
how much distribution of drug in blood to different parts of body
kidney 22%
liver (6% systemic
21% from GI)
muscle 15%
fat ~10%
brain 15%
values as % of co
what type of drugs accumulate in acidic en
how do you know if the drug has been eliminated?
if the drug does not return to the blood, it has then been eliminated
what are compartments?
the sum of all the tissues into which drugs distributes at approximately same rate
what happens when a drug penetrates tissues rapidly
it spreads instantly through this compartment
how can you for example form a compartment?
if there are two tissues with blood flow denoted by small arrows this means both tissues have slow penetration of drug and so the drug cannot spread instantly between this compartment
if
what is apparent volume of distribution?
amount of fluid needed to contain drug in the body at the same concentration as in the blood or the plasma
how big of an apparent volume of distribution would protein bound dugs trapped in plasma require?
small
what does a big apparent volume of distribution imply?
wide distribution of drug or extensive tissue binding or both
how big would the volume of distribution of protein bound drugs trapped in plasma be?
small
