Pharmacokinetics - Elimination

Question 1

Excretion of most drugs into sweat, saliva, tears, hair, and skin occurs only to a small extent but deposition of drugs in hair and skin has been used as a:

Answer 1

forensic tool in many criminal cases

Question 2

Elimination of drugs via the kidneys into urine involves the three processes of:

Answer 2

glomerular filtration
active tubular secretion
passive tubular reabsorption

Question 3

The glomerular filtration rate

Answer 3

125 mL/min

Question 4

the renal plasma flow is:

Answer 4

600 mL/min

Question 5

The glomerular filtration rate is normally about ____% of the renal plasma flow.

Answer 5

20%

Question 6

______ and _____ do not influence the passage of drugs into the glomerular filtrate

Answer 6

Lipid solubility and pH

Question 7

The passage of drug into glomerular filtrate is influenced by:

Answer 7

variation in glomerular filtration rate,

plasma binding of the drugs

Question 8

What can be done to minimize the back diffusion of drug from Nephric lumen to systemic circulation?

Answer 8

Manipulating pH of urine.

to increase the ionized form of the drug as only non polar drug can diffuse out

Question 9

weak acids can be eliminated by ________ of the urine

Answer 9

alkalinization

Question 10

weak bases may be increased by _____ of the urine

Answer 10

acidification

Question 11

The process to manipulate pH of urine to promote drug clearance is based on:

Answer 11

ion trapping

Question 12

Person with phenobarbital (weak acid) overdose can be given:

Answer 12

bicarbonate

Question 13

In amphetamine overdose, acidification of the urine with ____ leads to protonation of the drug.

Answer 13

NH4Cl

Question 14

Other less common routes of drug clearance include via:

Answer 14

intestines, the bile, the lungs, and milk in nursing mothers

Question 15

The lungs are primarily involved in the elimination of

____

Answer 15

anesthetic gases

e.g. halothane and isoflurane

Question 16

Excretion of most drugs into sweat, saliva, tears, hair, and skin occurs only to a small extent but deposition of drugs in hair and skin has been used as a:

Answer 16

forensic tool in many criminal cases

Question 17

The total body (systemic) clearance, CLtotal or CLt, is

Answer 17

the sum of the clearances from the various drug-metabolizing and drug-eliminating organs.

Question 18

Total clearance can be calculated as:

Answer 18

CLtotal = CLhepatic + CLrenal + CLpulmonary + CLother

Question 19

The half life of a drug is increased by:

Answer 19

1) diminished renal plasma flow or hepatic
blood flow,
e.g. in cardiogenic shock, heart failure, or hemorrhage;
2) decreased ability to extract drug from plasma
e.g. as seen in renal disease;
3) decreased metabolism,
e.g. when another drug inhibits its biotransformation or in hepatic insufficiency, as with cirrhosis.

Question 20

The half-life of a drug may decrease by:

Answer 20

1) increased hepatic blood flow,
2) decreased protein binding,
3) increased metabolism.

Question 21

A drug with a half-life of 12 hours is administered by
continuous intravenous infusion. How long will it take
for the drug to reach 90 percent of its final steady state level?
A. 18 hours.
B. 24 hours.
C. 30 hours.
D. 40 hours.
E. 90 hours.

Answer 21

D. 40 hours
A drug approaches 90 percent
of the final steady state in (3.3)(t1/2) = (3.3)(12) = ~40
hours.