Excretion/ Elimination

Question 1

Excretion

Answer 1

All drugs are ultimately eliminated from the body either being chemically altered (metabolized) or being intact or unchanged

Question 2

What is the most important route for many drugs?

Answer 2

Renal elimination/ excretion

Question 3

Net effect on elimination

Answer 3

Glomerular filtration and secretion (+) - enhances drug elimination into the urine
Reabsorption (-)- brings drug back into circulation

Question 4

Weak bases in urine

Answer 4

They ionize more and are less absorbed in acidic urine

Question 5

Weak acids in urine

Answer 5

Ionize more and less reabsorbed in the alkaline urine

Question 6

Glomerular filtration

Answer 6

Non-selective and unidirectional
All non-protein bound drugs

Question 7

Tubular secretion

Answer 7

Carrier-mediated process
Plasma protein has no effect

Question 8

Tubular reabsorption

Answer 8

Transported from tubular fluid back into capillary network
Takes place all along renal tubule
Increases half-life of drugs

Question 9

What is tubular reabsorption dependent on?

Answer 9

Urine flow rate
Lipid solubility of nonionized drug moiety
Urine pH

Question 10

Carnivores v. herbivores urine

Answer 10

Carnivores (pH 5.5-7.0)
Herbivores (7.0-8.0)
Species differences in urinary pH have a influence on rate of renal excretion of ionizable drugs

Question 11

A weakly _________ drug will have a higher renal excretion in herbivores

Answer 11

ACIDIC

Question 12

A weakly _______ drug will have a greater renal excretion in carnivores than herbivores

Answer 12

BASIC

Question 13

Hepatic elimination of drugs

Answer 13

Glucoronide conjugates are mainly and glutathione conjugates are exclusively excreted via bile

Question 14

How should drugs be in order to be excreted from bile?

Answer 14

Highly polar functional groups

Question 15

When is the liver’s ability to metabolize and excrete drugs reduced?

Answer 15

In acute liver diseases and chronic degenerative processes (cirrhosis)
SO the dose of drugs must be reduced in liver disorders

Question 16

Enterohepatic recycling

Answer 16

A drug from the systemic circulation is excreted into the bile and reabsorbed from small intestine back into bloodstream (prolongs drug (half-life)

Question 17

Why is Enterohepatic recycling important?

Answer 17

for enhanced activity of certain anti-parasitic drugs (avermectins)

Question 18

Other drug excretion sites/ routes

Answer 18

Liver –> bile
Skin –> sweat
Lung –> expired air
Lacrimal gland –> tears
Mammary gland –> milk
Salivary gland –> saliva

Question 19

Clearance total

Answer 19

Cl (total) = cl (renal) + cl (heaptic) + cl (others)