Renal Diuretics Flashcards
What do Diuretics cause?
Diuretics cause an increase in urine output (diuresis)
What do diuretics produce an increased excretion of?
Many diuretics also produce increased excretion of
Na (natriuresis) and K (producing hypokalaemia)
What are diuretics used in?
used in hypertension,
acute pulmonary oedema, heart failure
What are the 2 major groups of diuretics?
- Mainly affect H20 excretion
- Increase in electrolyte excretion
What is included in diuretics that mainly affect H20 excretion?
- Water
- Ethanol(Reduce ADH release)
- Osmotic diuretics
What is included in diuretics that cause an increase in electrolyte excretion?
- Carbonic anhydrase inhibitors
- Loop diuretics
- Thiazides
- K-sparing diuretics
What is the mechanism of action of diuretics on site 1?
Reabsorption of Na with passive movement of
organic molecules (glucose, amino acids) and H2O
What is the mechanism of action of diuretics on site 2?
Reabsorption of Na for H (Na/H exchanger) - Role of carbonic anhydrase
Where are both site 1 and site 2 located in the nephron?
Proximal convoluted tubule
Where is site 3 located in the nephron?
Loop of Henle
What is the mechanism of action of diuretics on site 3?
Transport of NaCl by a co-transporter for Na, K, 2Cl
-Interstitial fluid becomes hypertonic, aiding reabsorption of H20 from the collecting duct(controlled by ADH)
What is the permeability of thick ascending liip of henle to H20 like?
Thick ascending Loop of Henle is NOT permeable to H2O
Where are site 4, site 5 and site 6 located in the nephron?
Distal convoluted tubule
What is the mechanism of action on site 4 of diuretics?
Reabsorption of Na/Cl (co-transporter) followed by H2O
What is the mechanism of action on site 5 of diuretics?
Na is reabsorbed (through ENaC channels) in exchange for K efflux
(through K channels) - stimulated by aldosterone
What is the mechanism of action on site 6 of diuretics?
Na is reabsorbed and H+ lost via Na-H exchanger
- stimulated by aldosterone
What can an overactive site 5 produce?
Overactive Site 5 can produce K+ loss and plasma hypokalaemia
What can an overactive site 6 produce?
Overactive Site 6 can produce plasma alkalosis due to increased H+ excretion
What is an example of agent that mainly affect H20 excretion and how is it administred?
Mannitol
-Usually administered i.v.
How does mannitol work?
-High concentrations in plasma
-Causes increased osmolarity in tubules
-Results in decreased reabsorption of H20
Where does mannitol act at?
Acts at PCT, DCT, and collecting duct
What are the uses of mannitol?
-Reduce intracranial and intraocular pressure
-Prevent acute renal failure
-Excrete some types of poisoning
How does mannitol work to reduce intracranial and intraocular pressure?
-Mannitol does not enter the CNS
-Creates an osmotic gradient from cells to plasma
-H2O leaves the CNS (CSF into plasma)
-H2O leaves plasma into tubules and then urine
How do diuretics that affect electrolyte excretion work?
Drugs increase urine flow by increasing excretion of Na (natriuresis)
– where Na goes H2O follows (osmosis)
