Renal

Question 1

What are the 2 routes of drug excretion by the kidney?

Answer 1

1. Filtered at level of glomerulus - protein dependant 2. Actively secreted into renal tubule - protein independant

Question 2

Name 3 ion transporters that aid in actively secreting drug into tubule

Answer 2

1. organic anion transporters (OATs)
2. organic cation transporters (OCTs)
3. P-glycoprotein transporters (P-gP)

Question 3

What can influence renal excretion?

Answer 3

• renal disease
• age
• competition between drugs
• pH of urine (ion trapping)

Question 4

Describe the distribution in the body of a drug that is a weak acid

Answer 4

• the uncharged form equiliibriates between obdy compartments and equally distributes
• not much dissociation in stomach due to acidic environment
• plasma, more neutral than stomach, equilibrium shifts to right, more dissociation in plasma
• weak acids trapped in urine, highly dissociates and charged form can’t diffuse back to plasma so is excreted

Question 5

Describe the distribution of a drug in the body that is a weak base

Answer 5

• acid environment of stomach, highly dissociates, trapped in stomach compartment
• less dissociation in urine due to slightly alkaline environment
• equal concentration of uncharged form in all compartments

Question 6

How can the pH of urine be influenced?

Answer 6

• bicarbonate - increases pH
• ammonium chloride - decreases pH
• species - carnivore = 5.5-5.0

                   - herbivore = 7.0 - 8.0

Question 7

Describe 2 consequences of ion trapping

Answer 7

1. milk traps basic molecules - can pass drug onto new born, issue in dairy industry
2. plasma conc. can influence movement across the blood brain barrier - safety implications, useful in inflammatory conditions e.g. meningitis

Question 8

Name 4 drugs whose target organ is the kidney

Answer 8

• Frusemide - diuretic of choice in sm animal medicine
• Erythropoeitin - treat anaemia as result of CRF
• Benazepril and Telmisartan - modulators of RAAS

Question 9

Define a diuretic

Answer 9

A substance that promotes production of urine

Question 10

What are the 5 classes of diuretics?

Answer 10

1. Loop
2. Thiazidine
3. Potassium sparing/aldosterone antagonists e.g. Amiloride
4. Osmotic
5. Carbonic anhydrase inhibitors

Question 11

Draw a picture of the nephron to indicate the area in which these classes of drugs act

Answer 11

Question 12

Describe the action of loop diuretics

Answer 12

• act on thick ascending loop
• inhibit Na/K/2Cl carrier protein in luminal membrane by combining with the Cl binding site
• so ions stay in lumen, water retained in tubule and urine volume increases

Question 13

Describe the action of K sparing drugs, e.g. amiloride

Answer 13

• act on collecting duct
• blocks luminal Na channels
• indirectly decreases K loss (not being exchanged for Na)
• Na and water are retained in tubule, urine volume increases