Factors Affecting Excretion Of Drugs

Question 1

Factors determining filtration in the kidneys

Answer 1

Molecular size- small drugs may pass freely
Charge-polar molecules can’t pass through the membrane
Protein binding - only free drugs can filter through kidneys

Question 2

Tubular secretion involves what compartments?

Answer 2

Blood, tubule cell, renal tubule

Question 3

Organic anion transporters transport?

Answer 3

weak acids

Question 4

Organic cation transporters transport?

Answer 4

weak bases

Question 5

Drugs in distal tubular reabsorption
What can pass through and what remains?

Answer 5

Lipophilic drugs can freely pass in the tubules
Polar drugs remain in tubule
Most H2O is reabsorbed by the time it reaches the distal tubule - drugs concentration = high

Question 6

Proton donors are weak acids / bases?

Answer 6

Weak acids

Question 7

Proton acceptors are weak acids / bases?

Answer 7

Weak bases

Question 8

Weak acids more likely to be ionised in acidic /alkaline urine?

Answer 8

Alkaline

Question 9

Weak bases more likely to be ionised in acidic /alkaline urine?

Answer 9

Acidic

Question 10

CO2 + H20 in equilibrium (-) =

Answer 10

• H2CO3: EQUILIBRIM : H+ + HCO3-

Question 11

Explain acid-base homeostasis
- bicarbonate reabsorption

Answer 11

• HCO3 arrives in the the tubule having been filtered
• H+ is pumped out of the tubule cell into the lumen of the collecting system
• combines with HCO3-
• broken down into H2O + CO2
• these molecules can pass freely(non-polar)
• the reverse reaction then occurs and HCO3- is pumped back into the bloodand the H+ can be recycled

Question 12

Normal urine pH range?

Answer 12

4.5-7.8

Question 13

Disease
Acute conditions commonly reduce filtration via?

Answer 13

Reduced flow to kidney
Damage to tubule
Outflow obstruction

Question 14

Hepatic transporters can deliver drug or its metabolites into?

Answer 14

Bile

Question 15

Main route of elimination for larger molecules?

Answer 15

Bile

Question 16

Reversal of metabolic pathway can occur in?

Answer 16

In the intestine and active drugs can be reabsorbed
= Enterohepatic circulation, prolong duration of action of the drug

Question 17

Biliary/hepatic excretion influencing factors:

Answer 17

• Disease states: acute /chronic liver disease = alter efficiency of metabolic processes, drug elimination may be reduced
• Drug interaction (induce/inhibit CYP450 enzyme system

Question 18

Drug that induce CYP450 enzyme has what effect on drug concentration?

Answer 18

Induce- increased drug metabolism = lower drug concentration

Question 19

Drug that inhibit CYP450 enzyme has what effect on drug concentration?

Answer 19

Decreased drug metabolism - greater drug concentration

Question 20

can Diueretics or drinking lots of water can have an influence in urine/ filtrate flow?

Answer 20

yes but Not clinically important

Question 21

Sepsis can have what type of effect on drugs?

Answer 21

increase Renal clearance

Question 22

Role of kidneys in systemic pH homeostasis?

Answer 22

• Reabsorption of bicarbonate ( HC03-)
  -Excretion of acid/ production of HC03-

Question 23

Renal excretion: additional factors list some

Answer 23

filtrate/urine flow
disease states
drug interactions
metabolism