Drugs acting on the kidney

Question 1

What does thiazide act on?

Answer 1

Inhibition of Na+, Cl- co-transport in early distal convoluted tubule

This inhibits reabsorption of Na+ and Cl-

Indirectly increases reabsorption of Ca++

Question 2

Where and how does carbonic anhydrase inhibitors act?

Answer 2

Proximal tubules
Inhibit bicarbonate reabsorption (due to charges, is a secondary mechanism that prevents reabsorption of sodium)

Question 3

Where and how does loop diuretic act?

Answer 3

Thick ascending limb of loop of Henle

Inhibition of Na+/K+/2Cl- (NKCC2) co-transporter –> decrease in Na+ and Cl- reabsorption

Question 4

Why is there potassium loss in using thiazide diuretics?

Question 5

Where does K+ sparing diuretics act and how?

Answer 5

Late DCT and Collecting duct

They antagonise aldosterone leading to:
1) Inhibition of sodium absorption
2) Inhibition of potassium secretion

Question 6

Describe the electrolyte transport system in thick ascending limb of LoH.

Answer 6

Question 7

What are contraindications for thiazide diuretics?

Answer 7

Hypotension
Gout
Renal failure
Lithium therapy
Hypokalaemia
May worsen diabetes

Question 8

How does digoxin toxicity tie in with use of loop/thiazide diuretics?

Answer 8

Both diuretics predispose to hypokalaemia

MoA of Digoxin - …

Hypokalaemia further potentiates the effect of digoxin, leading to high likelihood of arrhythmias

Question 9

What is the effect of aldosterone?

Answer 9

It is secreted in response to hyponatraemia, it increases the expression of both Na/K ATPase and epithelial sodium channel, increasing reabsorption of sodium at the expense of secreting K+