Diuretics Flashcards
Mechanism of thiazide diuretics?
Inhibit SODIUM REABSORPTION at the distal convoluted tubule, by blocking the thiazide-sensitive Na+-Cl symporters.
What used to be the main indication for thiazide diuretics? What is now used instead?
Management of HTN, but now thiazide-like diuretics are recommended instead e.g. indapamide.
Example of thiazide diuretic?
bendroflumethiazide
How does bendroflumethiazide affect:
a) sodium
b) potassium
c) calcium
d) uric acid
a) hyponatraemia
b) hypokalaemia
c) hypercalcaemia
d) hyperuricaemia
How do thiazide diuretics cause hypokalaemia?
Due to increased delivery of sodium to the distal part of the distal convoluted tubule → increased sodium reabsorption in exchange for potassium and hydrogen ions.
Sodium reabsorption is then inhibited.
What is a key benefit of bendroflumethiazide causing hypercalcaemia?
Results in hypocalciuria –> decreases incidence of renal stones.
How do thiazide diuretics increase risk of gout?
As they increase direct urate reabsorption in the proximal renal tubules –> raised serum uric acid –> gout.
Key adverse effects of thiazide diuretics?
- hyponatraemia
- hypokalaemia
- hypercalcaemia
- hyperuricaemia
- gout
- impaired glucose tolerance
- impotence
Rare:
- thrombocytopaenia
- agranulocytosis
- photosensitivity rash
- pancreatitis
What can potassium-sparing diuretics be divided into?
1) epithelial sodium channel blockers –> amiloride and triamterene
2) aldosterone antagonists –> spironolactone and eplerenone
Why should potassium sparing diuretics be used with caution in patients taking ACEi?
As they precipitate hyperkalaemia.
Indications for aldosterone antagonists e.g. spironolactone?
1) ascites
2) HF
3) nephrotic syndrome
4) Conn’s syndrome
Why are aldosterone antagonists indicated in ascites?
Patients with cirrhosis develop a secondary hyperaldosteronism.
