Drug Elimination

Question 1

Excretion

Answer 1

Removal of drugs or metabolites from the body.

Question 2

Elimination

Answer 2

Excretion or inactivation of drug by metabolism

Question 3

Hydrophilic drugs

Answer 3

can be excreted via urine w/out metabolism

Question 4

Kidneys

Answer 4

Major route of excretion of most drugs.
Most have to be metabolized b4.
High blood flow
Clears blood of drug by FILTRATION and ACTIVE SECRETION

Question 5

The three processes that predominate excretion via the kidney;

Answer 5

Filtration, Reabsorption, Secretion

Question 6

Filtration via the kidney

Answer 6

Same clearance of plasma compounds (creatinine is classic clearance substance).

Question 7

What is favoured to be excreted by the kidney?

Answer 7

Polar drugs and metabolites

The low pH of urine traps weak bases, which can speed up elimination/detox.

Question 8

Secretion via the kidney

Answer 8

Some drugs secreted into proximal tubules.

Penicillin 90% of elimination is secretion.

Question 9

Secretion results:

Answer 9

Rapid elimination and high concentrations in bladder.

Question 10

In the liver:

Answer 10

Elimination: deactivates through metabolism.
Prepars many lipophilics for renal excretion.
Prepares some drugs for biliary excretion.

Question 11

Hepatic metabolism/biotransformation:

Answer 11

Enzymes breakdown or transform drug molecules.

Question 12

Elimination by the liver

Answer 12

Can secrete drugs or its metabolites into bile which is then secreted into intestines.

Question 13

Enterohepatic cycling:

Answer 13

most of what is secreted with the bile into the intestines is reabsorbed by the intestines.

Question 14

Unabsorbed drugs or drugs not reabsorbed:

Answer 14

Go out with feces.

Question 15

Elimination by lungs

Answer 15

Important for elimination of general anesthetics.

Lungs eliminate gases and not much else

Question 16

Measuring elimination

Answer 16

Most commonly used measure ishalf life.

Question 17

Clearance

Answer 17

Theoretical amt of blood totally cleared of drug in a given time.
mL/min
Only drugs w 1st order elimination have constant clearance rate.

Question 18

Half-life determined by

Answer 18

Clearance and volume of distribution
t1/2=(Vd*0.7)/Cl
Cl is a measure of the function of elimininating organ.
Vd is a measure of the fraction of drug in blood

Question 19

Clearance (defines)

Answer 19

Defines the rate at which a drug must adminstered to achieve a desired concentration

Question 20

Renal clearance

Answer 20

If a drug has a Cl of approximately 120 ml/min has a rate of elimination roughly equivalent to filtration: no reabsorption, no tubal secretion.
If a drug has a Cl of approximately 720 ml/min it has a rate of elimination roughly equivalent to renal plasma flow=tubal secretion, no reabsorption.

Question 21

1st order elimination

Answer 21

Almost all drugs.
The amt of drug eliminated proportional to concentration in blood.
Fraction of drug eliminated is constant.
Constant half-life
If it is decreased at t1/2 by 1/3 it will keep doing so at hour two, three, four, etc.

Question 22

Zero order elimination

Answer 22

Like alcohol
No half life
Constant amt eliminated over time

Question 23

Zero order elimination details

Answer 23

[Drug] overwhelms mechanism of elimination.
Only very few drugs that are effective at high concentrations., or drugs at toxic concentrations.
Since it has no constant half life, if it is eliminated at a 100ug/ml/hr it will do so forever.