T3 L6: Diuretic agents Flashcards
What is the definition of a diuretic agent?
A drug that increases excretion of both fluids and solutes
What is Natriuretic excretion?
Of Na+
What is Kaliuretic excretion?
Of K+ (usually an unwanted effect)
Where do carbonic anhydrase inhibitors take effect as diuretics on a nephron?
Proximal tubule (not powerful)
Where do osmotic diuretics take effect on a nephron?
Proximal tubule and descending loH (water permeable parts of the nephron)
Where do loop diuretics take effect on a nephron?
Ascending loH
Where do thiazides and thiazide-like diuretics take effect on a nephron?
Early distal tubule
Where do potassium-sparing diuretics (aldosterone antagonists and non-aldosterone antagonists) take effect on a nephron?
Late distal and early collecting tubule (They’re weak)
How do loop diuretics work?
They inhibit NKCC2 transporters in the thick ascending limb of the loH so reabsorption of Na+, K+ and Cl- increases. They are the most effective diuretics available
How does weighing yourself prevent dehydration when using diuretics?
If they gain weight, they need to drink less and if they lose weight then they need to drink more
What are some clinical uses of loop diuretics?
Acute pulmonary oedema, chronic heart failure, cirrhosis of the liver, resistant hypertension, nephrotic syndrome, and acute kidney injury
What are some unwanted effects of loop diuretics?
Dehydration, Hypokalaemia, metabolic alkalosis due to loss of H+ in urine, Hypokalaemia can potentiate effects of cardiac glycosides, and deafness when used with aminoglycoside antibiotics
How do loop diuretics cause hypokalaemia?
They increase the exchange of Na+ for K+ in the distal tubule
How do Thiazide diuretics work?
They inhibit apical Na+/Cl- co-transporters in the distal tubule and therefore cause increased Na+ excretion with increased water excretion. They last up to 24hours
What is the main thiazide diuretic and what is it used for?
Bendroflumethiazide used for mild/moderate heart failure
What is indapamide used for?
Resistant hypertension because it has less side effects
What are thiazide diuretics used for?
Hypertension, oedema, and mild heart failure
What are some unwanted effects of thiazide diuretics?
Hypokalaemia, metabolic acidosis, gout, hyperglycaemia as they have an effect on pancreatic beta-cells, increased plasma cholesterol with long-term use, and male impotence that’s reversible
What’s the mechanism behind metabolic acidosis?
Loss of urinary H+
What is gout?
Increased plasma uric acid
Why do thiazide diuretics cause gout?
They work on the transporter that transports uric acid in the nephron
What are the symptoms of mild hypokalaemia?
Fatigue, drowsiness, dizziness, muscle weakness
What are the symptoms of severe hypokalaemia?
Abnormal heart rhythm, muscle paralysis, and death
How do potassium-sparing diuretics work?
They inhibit Na+ reabsorption on the distal tubules where K+ is not secreted
