Session 7 - Diuretics Flashcards
Define diuresis
• Increased formation of urine by the kidney
Define diuretics
• Block reabsorption of Na+ and therefore water by the kidney
Give three main types of diuretics
- Loop diuretics
- Thiazide diuretics
- K+ sparing diuretics and aldosterone antagonists
How do loop diuretics work?
- Acts on TAL of the loop of henle
- Block Na-K-2Cl
- Causes excretion of 10-25% of filtered Na+ ions (segments downstream also have limited capacity to reabsorb water, increasing diuresis)
Name two loop diuretics
- Furosemide
* Bumetanide
What do Thiazide diuretics do?
- Act on early DCT
- Block Na-Cl co-transporter
- Inhibits only 5% of Na+ reabsorption
Give a thiazide diuretic
• Bendroflumethiazide
Where do K+ sparing diuretics and aldosterone antagonists work?
- Late DCT and collecting duct
- Reduce ENaC reabsorption of sodium
- Inhibit 2% Na+ reabsorption
Why are K+ sparing diuretics named thus?
Reduce the loss of K+ and can produce life threatening hyperkalaemia
Give an example of a K+ sparing diuretic
• Amiloride
Give an example of an aldosterone antagonist
• Spironolactone
Give overall dangers of diuretics
- Hyper/hypokalaemia
* RAAS activation
Outline the negatives of using K+ sparing diuretics/Aldosterone Antagonists
• Reduce loss of K+ and may produce life threatening hyperkalaemia
Give a negative effect of loop diuretics
• Reduces calcium absorption, inducing urinary excretion
Patient may become hypocalcaemi
What do loop and thiazide diuretics do?
• Increase the loss of potassium in the urine
Hypokalaemia
Outline how loop and thiazide diuretics cause hypokalaemia
- Block Na+ and H20 reabsorption in LoH or early DCT
- Increase Na+ and H20 delivery to late DT + CD
- Increase Na+ absorption by principle cells/Faster flow rate of filtrate so K+ washed away faster
- Favourable electrical gradient for K+ excretion/Low K+ concentration in lumen
How do K+ sparing diuretics cause hyperkalaemia?
- Block epithelial Na+ channels
- Reduce Na+ reabsorption
- Reduce potassium loss in urine
- Hyperkalaemia
How do aldosterone antagonists cause hyperkalaemia?
- Block of action of aldosterone
- Reduce activity of Na/K+ ATPase & epithelial Na+ channels
- Reduce Na+ reabsorption
- Reduce potassium loss in urine
- Hyperkalaemia
What do all diuretics do?
- Reduce ECF volume so activate RAAS
* This increases aldosterone secretion, increase Na+ reabsorption and K+ secretion, contributing to hypokalaemia
List negative effects which come about as a result of diuretics use and abuse
- Hypokalaemia
- Hyperkalaemia
- RAAS activation
- Hypovolaemia
- Hyponatraemia
- Increased uric acid levels in blood
- Metabolic effects
What is hypovolaemia?
• Decreased ECF volume due to excessive loss of Na+ and water
What 3 things must be done to avoid hypovolaemia?
- Monitor weight
- Look for signs of dehydration
- Check BP
What is hyponatraemia?
• Decreased sodium in blood
Multiple symptoms, including nausea, vomiting, headache and confusion
What do increased uric acid levels in blood cause?
Gout
