Excretion of Drugs

Question 1

5 routes of elimination:

Answer 1

kidney (urine-most common), liver (bile-feces), lungs, sweat/saliva, breast milk

Question 2

Different forms of renal elimination processes:

Answer 2

1. bulk flow via glomerular filtration
2. passive diffusion (distal tubule) (urine-blood)
3. Carrier-mediated transport (proximal tubule) (urine-blood)
4. Water reabsorption (loop of Henley)

Question 3

What types of molecules can/cannot be filtered by glomerular filtration?

Answer 3

CAN: small, ionic, non-ionic, lipophilic, hydrophilic
CANNOT: large molecules, protein (albumin) bound

Question 4

Filtration rate is dependent on:

Answer 4

renal blood flow and permeability

Question 5

What type of drugs use passive diffusion?

Answer 5

Nonionic and lipophilic

Question 6

Ionized drugs may be retained and eliminated in urine. T/F

Answer 6

TRUE.

Question 7

Reabsorbed from the tubule back to blood:

Answer 7

passive reabsorption low albumin-binding drugs

Question 8

Absorption from blood to tubule:

Answer 8

Passive secretion; high albumin-binding drugs

Question 9

What determines drug transport by passive diffusion?

Answer 9

lipid solubility of non-ionized form of drug, pKa of drug, weak acid or weak base, pH of urine

Question 10

If the urine is more acidic what will happen to excretion of weak acids and base?

Answer 10

decreased excretion of weak acid, increased excretion of weak base

Question 11

If the urine is more alkaline what will happen to the excretion of weak acids and base?

Answer 11

increased excretion of weak acid, decreased excretion of weak base

Question 12

Phenobarbital overdose, weak acid =

Answer 12

Na bicarbonate to increase pH of urine

Question 13

Amphetamine of PCP, weak bases =

Answer 13

Ammonium CI to lower pH of urine –> detox therapy

Question 14

Both ABCs and SLCs are found in the proximal tubule. T/F

Answer 14

TRUE

Question 15

What type of compounds are transport by proximal tubules?

Answer 15

larger, hydrophilic, ionized xenobiotics and endogenous compounds

Question 16

Transport from the blood to tubule:

Answer 16

tubular secretion

Question 17

Transport from tubule to blood:

Answer 17

tubular reabsorption

Question 18

Balance of renal transport favors what to the tubule?

Answer 18

secretion

Question 19

During carrier-mediated transport in renal excretion, there are more drugs where compared to where?

Answer 19

greater amount of drugs in proximal tubule than in the plasma

Question 20

______ type of transporters have a higher affinity for drugs than ______ transporters.

Answer 20

Secretory (efflux). reabsorption (re-uptake)

Question 21

How is metabolized drug transported from hepatocytes to blood or bile canaliculi?

Answer 21

active transporters

Question 22

Anionic, bile salt, cation, and neutral organic transporters are all examples of what general type of transporter?

Answer 22

active

Question 23

Biliary transporters are associated what kind of compounds?

Answer 23

polar, ionic, relatively large, high molecular weight