Lecture 4: Excretion

Question 1

major routes of excretion

Answer 1

-renal (primary)
-bile to feces

Question 2

other routes of excretion

Answer 2

-pulmonary
-salivary
-mammary

Question 3

Nephron

Answer 3

-primary functional unit of kidney
-compact

Question 4

mechanisms of renal excretion

Answer 4

-filtration
-active tubular secretion
-tubular reabsorption
-biotransformation

Question 5

Filtration location

Answer 5

-glomerulus

Question 6

tubular secretion location

Answer 6

-proximal convuluted tubule

Question 7

tubular reabsorption location

Answer 7

-distal convuluted tubule
-collecting duct

Question 8

Glomerular filtration

Question 9

Determinants of Filtration

Answer 9

-number of functional nephrons
-size (<5000)
-protein binding (permeability)
-renal blood flow (delivers drug to kidney)

Question 10

Old people have less nephrons

Answer 10

-reduce dose
-less excretion

Question 11

Renal Clearance vs weight graph

Answer 11

-negative slope
-increase weight decreases clearance rate

Question 12

Renal clearance vs Creatinine Clearance

Answer 12

-positive slope
-increase together

Question 13

Decrease creatinine clearance

Answer 13

-decrease renal clearance by filtration
= lower dose

Question 14

Active Tubular Secretion

Answer 14

-carrier-mediated transport
-some filtration still
-susceptible to competitive interactions
-stereoselective excretion

Question 15

carrier-mediated reactions (ATS)

Answer 15

1. saturable
2. competitive interactions (only certain amount of carriers available = drug interactions)

Question 16

dose vs excretion rate

Answer 16

-positive slope for filtration
-positive slope that levels off for ATS

Question 17

Tubular Reabsorption

Answer 17

-most passive
-some carrier-mediated

Question 18

passive tubular reabsorption

Answer 18

-driven by concentration gradient
-determined by lipophilicity and pKa
-influenced by urine flow and pH

Question 19

carrier-mediated (ACTIVE) reabsorption

Answer 19

-saturable (capacity-limited)
-ascorbic acid and glucose
-what shows up in urine is reabsorbed back into blood

Question 20

saturable

Answer 20

-increase concentration saturates reabsorption

Question 21

Urine vs blood drug concentration

Answer 21

-blood more accurate
-urine reabsorption leads to higher concentration
-why we use blood glucose for diabetes

Question 22

tubular/plasma concentration

Answer 22

1=same
>1: higher in tubule (creatinine)
<1: higher in blood (glucose)

Question 23

What happens to reabsorption as urine flow is INcreased?

Answer 23

-DEcrease reabsorption

Question 24

Why do some meds require u to drink lot of water

Answer 24

-drug can precipitate out if drug concentration is too high
-kidney stones

Question 25

Ascorbic acid

Answer 25

-undergoes REabsorption
-massive increase in dose barely increases plasma level
-bc ur saturating = spills out into the urine

Question 26

Biotransformation of drugs

Answer 26

-mostly liver but some in kidney (vitamin D)

Question 27

Vitamin D

Answer 27

-must be bioactivated to active form
-liver makes active form

Question 28

What is the most important determinant of filtration of a drug?

Answer 28

molecular weight

Question 29

How do passive and active tubular reabsorption differ?

Answer 29

-saturability
-need to look at variety of doses to see effect ?

Question 30

What occurs to secretion as blood concentration increases

Answer 30

-reach maximum secretion (saturation)

Question 31

Which types of drugs will have more drug interactions? (filtered or secreted?)

Answer 31

-secretion because of carriers
-carriers=competition