Excretion

Question 1

What is excretion?

Answer 1

The removal of a drug molecule from the body without chemical modification

Question 2

What % is elimination after IV administration?

Answer 2

100% as no metabolism has occured

Question 3

What is a typical GFR?

Answer 3

125ml/min

Question 4

What happens in Glomelular filtration?

Answer 4

Nephrons filter and only small particles pass through
Proteins cannot pass through

Question 5

What happens in tubular reabsorption?

Answer 5

Kidneys reabsorb nutrients back into the blood
Active form of drug will also be reabsorbed and inactive form will be excreted
Proteins can be excreted by secretion

Question 6

What type of drugs are effeciently excreted by the kidneys?

Answer 6

Very water soluble drugs - ionised

Question 7

What is active secretion?

Answer 7

Energy requiring
2 seperate mechanisms for acids and base
Can be competitive so drug interactions can occur

Question 8

What is ion trapping?

Answer 8

Ionised form of drug gets trapped on one side of a membrane
Weak acids and bases are in ionised and unionised form

Question 9

How can it be determined that active secretion is occurring?

Answer 9

Renal clearance is higher than GFR

Question 10

What does it mean if renal clearance is less than GFR?

Answer 10

Molecules haven’t been filtered or extensively reabsorbed

Question 11

What is creatinine?

Answer 11

A waste product formed continuously by muscle

Question 12

Creatinine

Answer 12

Filtered by kidneys
Almost no active secretion
Almost no reabsorption
Creatinine clearance is approximately equal to GFR