Unit 1- Excretion

Question 1

Most important route of drug elimination

Answer 1

renal excretion

Question 2

Factors determining renal excretion

Answer 2

Renal blood flow, active tubular secretion, tubular reabsorption

Question 3

Total renal excretion of a drug

Answer 3

Rate of filtration + secretion - reabsorption

Question 4

Glomerular Filtration

Answer 4

Determined by renal blood flow, drugs enter glomerulus from blood by bulk flow passively

Question 5

Active Tubular Secretion

Answer 5

Transport proteins at the brush border and basolateral membrane move drugs rapidly, not limited by protein binding, susceptible to competition between drugs

Question 6

Organic Anion Transporter

Answer 6

Secretory pathway in the renal tubules for acidic compounds

Question 7

Organic Cation Transporter

Answer 7

Secretory pathway in the renal tubule for basic compounds

Question 8

Competition in tubular transport

Answer 8

Many drugs compete for the same tubular transport sites, weak acids can inhibit secretion of other weak acids

Question 9

Tubular Reabsorption

Answer 9

Passive reabsorption from renal tubules into renal capillaries slows renal excretion, depends on lipid solubility and ionization

Question 10

Reabsorption and ionization

Answer 10

Weakly acidic drugs more likely to be reabsorbed in acidic urine but trapped and excreted in alkaline urine

Question 11

Diet and pH

Answer 11

Carnivores have more acidic urine than herbivores. Acidic drugs have higher renal excretion in herbivores, basic drugs have higher renal excretion in carnivores

Question 12

Modifying pH

Answer 12

Urinary pH can be altered to change renal excretion rate in cases of overdose or toxicity

Question 13

Urine Drug Concentration

Answer 13

Drugs that are not reabsorbed will concentrate in the renal tubule, leading to nephrotoxicity

Question 14

Polar Compounds and Reabsorption

Answer 14

Polar compounds have low lipid solubility and are not reabsorbed, many drug metabolites

Question 15

Active Reabsorption

Answer 15

Systems used to recover essential nutrients, drugs that are actively reabsorbed have important tubular fluid concentration for predicting activity

Question 16

Factors affecting Active Secretion

Answer 16

Renal blood flow, drug pKa

Question 17

Factors affecting Glomerular Filtration

Answer 17

Molecular weight, protein binding, renal blood flow

Question 18

Factors affecting Passive Reabsorption

Answer 18

Drug concentration, molecular weight, lipid solubility, drug pKa, urine pH

Question 19

Renal Biotransformation

Answer 19

Phase I and phase II enzymes exist in the kidney, oxidative processes occur in proximal tubule

Question 20

Relay Metabolism

Answer 20

The kidney metabolizes a drug already biotransformed by the liver

Question 21

Other routes of excretion

Answer 21

Bile, milk, saliva, expired air, feces, sweat, tears

Question 22

Biliary Excretion I

Answer 22

Drugs excreted in bile are in contact with intestine and its flora, causing adverse reactions, phase II drugs may undergo enterohepatic circulation, intestinal bacteria can unconjugate the drug

Question 23

Enterohepatic Circulation

Answer 23

Drugs are conjugated in the liver and eliminated in the bile, bur unconjugated in the small intestine and reabsorbed, the drug then reenters systemic circulation and prolongs half-life

Question 24

Saliva Excretion

Answer 24

Drugs enter saliva by passive diffusion from the blood, important in herbivores that have large amounts of saliva that can be swallowed and upset digestion

Question 25

Expired Air Excretion

Answer 25

Important for volatile drugs

Question 26

Milk Excretion

Answer 26

Weakly basic drugs may distribute into milk after systemic distribution, important if milk is for human consumption

Question 27

Feces Excretion

Answer 27

Drugs nor absorbed after oral administration or secreted through intestines are excreted in feces

Question 28

Elimination

Answer 28

Combined effects of hepatic metabolism, renal excretion, and biliary excretion irreversibly clears the drug from the body

Question 29

Pediatric

Answer 29

The first 12 weeks of life

Question 30

Neonatal Physiology

Answer 30

Decreased hepatic metabolism, immature biliary function, decreased GFR, decreased renal clearance