Pharmacology: Diuretics

Question 1

What are the roles of the kidney?

Answer 1

REEM
R: regulatory - fluid, acid-base, electrolytes
E: excretory - wastes, drug elimination via glomerular filtration or tubular secretion
E: endocrine - RAAS, erythropoetin, prostaglandins
M: metabolism - vit D, insulin, PTH

Question 2

List the classes of drugs acting on the renal tubules

Answer 2

Diuretics:

• carbonic anhydrase inhibitors
• osmotic diuretics
• loop
• thiazides
• potassium sparing

Others:

• aldosterone antagonists
• ADH antagonists

Question 3

What are some generic ADRs of diuretics

Answer 3

• anaphylaxis
• hypovolaemia and hypotension leading to acute renal failure
• electrolyte disturbance
• metabolic abnormalities

Question 4

What are some common ADRs of thiazides?

Answer 4

• gout

- erectile dysfunction

Question 5

What are some common ADRs of spironolactone?

Answer 5

Hyperkalaemia

Painful gynaecomastia

Question 6

What are some common ADRs of furosemide?

Answer 6

Ototoxicity - can lead to ringing, pain, hearing loss

Nephrotoxic

Question 7

Give some reasons why diuretic therapy may not be effective

Answer 7

• primary cause not treated
• continuation of high sodium intake
• poor adherence
• poor absorption
• volume depletion can decrease filtration of diuretics
• volume depletion increases aldosterone which increases Na reab
• NSAIDs can reduce renal blood flow

Question 8

What are the major indications for diuretics?

Which drugs would be most appropriate?

Answer 8

Heart failure:
Give loop or thiazide diuretics
(also give B blockers and ACEI)

Hypertension:
Give thiazide or spironolactone
( also give B blockers and ACEI)

Decompensated liver disease:
Give spironolactone or loop

Question 9

List some potentially nephrotoxic drugs

Answer 9

ACEI
Aminoglycosides eg gentamycin 
Penicillins 
Cyclosporin 
Metformin 
NSAIDs

Question 10

What are the ECG changes seen in hyperkalaemia?

Answer 10

Early: tall T wave with narrow base, prolonged PR
Mid: loss of P wave, broad QRS, ST elevation, ectopic beats
Late: VF, asystole, axis deviation

Question 11

What are the ECG changes seen in hypokalaemia?

Answer 11

Depressed ST segment
Biphasic T wave
U wave

Question 12

How is hyperkalaemia managed?

Answer 12

Find the cause and do an ECG.
Treatment:
- give calcium gluconate to protect the heart
- insulin + dextrose to enhance uptake of glucose and potassium into the cells
- give calcium resonium to absorb the K+
- give sodium bicarbonate to counteract acidosis