PHARMACOLOGY - Renal Pharmacology

Question 1

What allow plasma protein bound drugs to be secreted into the tubular lumen?

Answer 1

Organic anion transporters (OAT)
Organic cation transporters (OCT)
P-glycoproteins (PgP)

Question 2

Why is drug metabolism in the liver so important in terms of renal excretion of drugs?

Answer 2

Drug metabolism increases the water solubility of the drug, increasing the chance that the drug will be excreted in the urine

Question 3

What are the four main influences on renal excretion of drugs?

Answer 3

Renal disease
Elderly patients
Competition between drugs
Urine pH

Question 4

Describe how competition between drugs can impact the renal excretion of these drugs

Answer 4

If two drugs need to be secreted into the renal tubules by the same transporter proteins, the transporter can become saturated and thus impair the excretion of one or both of these drugs

Question 5

What is ion trapping?

Answer 5

Ion trapping is the build up of a higher concentration of a chemical across a cell membrane due to the pKa value of the drug and the difference of pH across the cell membrane

Question 6

How does ion trapping affect drug distribution around the body?

Answer 6

Ionised drugs are not absorbed as efficiently as un-ionised drugs are so ion trapping leads to an uneven distribution of the drug around the body depending the pKa value of the drug

Question 7

In which environment is ionisation of a weak acid at its optimum?

Answer 7

Ionisation of a weak acid is greatest at an alkaline pH (i.e. in the urine)

Question 8

In which environment is ionisation of a weak base at its optimum?

Answer 8

Ionisation of a weak base is greatest at an acidic pH (i.e. in gastric fluid)

Question 9

How does ion trapping affect lactation?

Answer 9

Milk is acidic relative to plasma so weak base molecules will become trapped within the milk and thus be passed onto the neonate through suckling or into the consumer market in the dairy industry

Question 10

How can manipulating the urine pH effect drug pharmacodynamics?

Answer 10

Manipulating the urinary pH influences the clearance of the drug from the body. The slower the rate of clearance, the longer the drug will remain in the bloodstream and the longer the pharmacodynamic effects of the drug will last

Question 11

What can be administered to increase the urinary pH?

Answer 11

Bicarbonate

Question 12

What can be administered to decrease the urinary pH?

Answer 12

Ammonium chloride

Question 13

How does the urine pH vary between carnivores and herbivores?

Answer 13

Carnivores: 5.5 - 7.0 pH
Herbivores: 7.0 - 8.0 pH

Question 14

What are diuretics?

Answer 14

Diuretics are substances used to promote urine production (i.e. increase water and electrolyte excretion)

Question 15

Give an example of a loop diuretic used commonly in small animal practice

Answer 15

Frusemide

Question 16

What is the mechanism of action of Frusemide?

Answer 16

Frusemide inhibits the Na+/K+/Cl- co-transporter on the apical membrane of the thick ascending loop of Henle, promoting the excretion of Na+ and water through inhibiting their reabsorption

Question 17

With long term use, Frusemide can lead to the excessive excretion of K+, thus causing complications. Give an example of a K+ sparing diuretic that can be given in combination with Frusemide to prevent this

Answer 17

Amiloride

Question 18

What is the mechanism of action for Amiloride?

Answer 18

Amiloride inhibits the Na+ transporter on the apical membrane of the collecting duct, inhibiting Na+ reabsorption without depleting K+