Urinary pharmacology Flashcards
What do diuretics do? How do they work?
Increase output of urine
Excrete sodium and water to prevent retention
Diuretics can be direct or indirect. How do these diuretics work?
Direct - acts on cell of the nephron
Indirectly - modify filtrate content
What is a common problem with diuretics? Why?
Hypokalaemia
Potassium lost with sodium
What are the 5 groups of diuretics?
Osmotic diuretics Potassium sparing diuretics Loop diuretics Carbonic anhydrase inhibitors Thiazides
Are osmotic diuretics direct or indirect? How do they work?
Indirect
Alter concentration of filtrate - they are filtered through the glomerulus but not reabsorbed so alter osmotic pressure in the nephron
What effect does an increased amount of filtrate have on sodium reabsorption?
Increased filtrate = less sodium reabsorption
Give an example of an osmotic diuretic?
Mannitol
How are osmotic diuretics administered?
IV
What are osmotic diuretics used for?
Olguric renal failure (can’t urinate)
Cerebral oedema
Glaucoma
Forced diuresis if poisoned
What is a side effect of an osmotic diuretic?
Initial increase in ECF
Can worsen oedema or cardiac failure
Where is carbonic anhydrase? What is the function of carbonic anhydrase?
In PCT, eyes and RBCs
Dissociates carbonic acid to produce H+
How do carbonic anhydrase inhibitors work? How is ionic balance maintained?
Inhibit carbonic anhydrase
Decrease H+ production and reduced Na/H+ exchange
Cl- retained to maintain ionic balance
What affect do carbonic anhydrase inhibitors have on the pH of urine?
Make it alkalotic
How are carbonic anhydrase inhibitors administered?
Orally
What are carbonic anhydrase inhibitors used to treat?
Oedema
Not used directly as a diuretic but have that effect
What are the adverse effects of carbonic anhydrase inhibitors?
Metabolic alkalosis
PUPD
When can’t carbonic anhydrase inhibitors be used and why?
Liver disease
Alkaline urine means NH4 produced in kidneys goes into circulation
Which diuretics are the most powerful?
Loop diuretics
How do loop diuretics work?
Inhibit Na/K/Cl ransport in the LOH
Increase delivery of Na to DCT
Increase excretion of K, H+, Mg and Ca2+
How are loop diuretics administered?
Orally
Parenterally
What are loop diuretics used to treat?
Oedema
Congestive heart failure
What are the adverse effects of loop diuretics?
Dehydration
Hypovolaemia if no water access
Hypokaelmia
ECF disturbances
Thiazides are less powerful diuretics. Why are they still used?
Less side effects
Oedema
Dissolution of calcium containing bladder/kidney stones
How do thiazides work?
Inhibit Na/Cl co-transport before aldosterone stimulated Na/K exchange
Increase Na, Cl, Mg and K excretion
Decrease calcium excretion
Are loop diuretics more powerful diuretics than thiazides? Why?
Loop diuretics more powerful
Majority of Na has been reabsorbed in thiazides
What are the adverse effects of thiazides?
Hypokalaemia Dehydration Hypovolaemia if no water access ECF disturbances (less severe than loop diuretics) Hyperglycaemia
How are thiazides administered?
Orally
Are potassium sparing diuretics powerful? When are they used?
Not when used alone
Used with loop diuretics and thiazides to prevent hypokalaemia
How do potassium sparing diuretics work?
Affect Na but not K
2 ways: competitive inhibitors of aldosterone or inhibitors of Na reabsorption (therefore more Na/K/ATPase activity)
What are the adverse effects of potassium sparing diuretics?
Hyperkalaemia
When should potassium sparing diuretics not be used?
Renal impairment
Diabetes
Metabolic acidosis
Don’t use more than one together!
What are potassium sparing diuretics used for?
Oedema
Preventing hypokalaemia
Why can different diuretics be used together?
Sequential nephron blockade - act at different points in the nephron
How are potassium sparing diuretics administered?
Orally
