Drug Distribution

Question 1

factors that determine drug distribution

Answer 1

plasma protein binding - only unbound drugs are active ie from 98% bound to 96% bound gives 100% increase in active drug

tissue perfusion

membrane characteristics - blood-brain barrier, blood-testes/ovary barrier

transport mechanism

diseases/ other drugs

elimination

Question 2

Renal drug excretion - Glomerular filtration

Answer 2

all unbound drugs are filtered at the glomerulus provided their size or charge doesn’t prevent this

anything that affects filtration rate will affect the filtration rate will affect the clearance rate of a drug

Question 3

renal drug excretion - Passive tubular reabsorption

Answer 3

as the filtrate moves down the tubules of the kidney, it become more concentrated as do any drugs it carries

passive diffusion means that the body can reabsorb some of this drug

only un-ionised drug can be absorbed

can also be affected by renal failure

Question 4

renal drug excretion- Active tubular secretion

Answer 4

some drugs are actively secreted into the proximal tubules of the kidneys

main method of excretion for protein bound cationic and anionic drugs