Diuretics Flashcards
T/F: Diuretics cause urination.
False. They increase urine volume/urine flow.
How is sodium excreted from the body due to diuretics?
as NaCl
Are cardiovascular and physiological diuretics true diuretics?
No, they just have a diuretic effect.
T/F: the action of cardiovascular diuretics on the kidneys is secondary.
True. Their diuretic effect is primarily because of their action on the heart.
When is dopamine considered a diuretic?
at low doses only. Acts on the cholinergic receptors and increases renal blood flow.
What is the therapeutic use of cardiovascular diuretics?
To treat edema associated with congestive heart failure.
What is the site of action of ADH?
The collecting ducts.
What are the 2 physiologic diuretics?
Water and sodium chloride.
When is sodium chloride used as a diuretic?
In urolithiasis in calves, cats, and sheep
T/F: carbonic anhydrase inhibitors are used as diuretics.
False.
What is the most commonly used osmotic diuretic?
Mannitol
T/F: Mannitol will act as a diuretic when given IV and PO.
False. It will not act as a diuretic when given PO.
What is the most effective class of diuretics and where do they act?
loop diuretics, act on the thick ascending loop of henle.
How much tubular reabsorption of Na occurs in the TAL?
25%
What is the second most effective class of diuretics and where do they act?
Thiazide diuretics, act on the early distal tubules.
How much Na reabsorption occurs in the early distal tubules?
5%
What are the third most effective class of diuretics?
osmotic diuretics and carbonic anhydrase inhibitors (but carbonic anhydrase inhibitors are not used as diuretics)
What is the mechanism of action of Mannitol?
acts in the loop of Henle and in the proximal tubule (secondary) pulling water along with it into the interstitial space.
What is mannitol used to treat?
localized edema or acute glaucoma. Can also be used to treat acute renal failure.
When is mannitol contraindicated?
in generalized edema or when there is cerebral hemorrhage.
T/F: Mannitol crosses the eye barrier and the blood brain barrier.
False
Why can mannitol also be used to treat acute renal failure?
because it increases renal blood flow and renal medullary blood flow by several mechanisms.
T/F: mannitol is metabolized and then eliminated rapidly by the kidneys.
False. mannitol is not metabolized.
T/F: all loop diuretics are weak acids
True
With the exception of ____, diuretics are given orally. ___ diuretics are oral and injectable.
Mannitol, loop diuretics.
What is the most common loop diuretic?
furosemide.
what is the primary mechanism of action of loop diuretics?
inhibit the Na+/K+/2Cl- symporter at the luminal membrane in the thick ascending limb of the loop of Henle.
What 3 drugs can you use to treat acute renal failure?
mannitol, loop diuretics (furosemide), and dopamine.
What is the secondary mechanism of action of loop diuretics and why is it important?
Causes more secretion of Ca+ and K+. It is important because the secretion of potassium can cause hypokalemia, leading to tachycardia, tachyarrhythmias, and death. The added excretion of Ca2+ can be used to treat hypercalcemia.
T/F: loop diuretics lower blood pressure via vasodilation.
True
What gives loop diuretics their ability to vasodilate?
the increase they cause in systemic venous capacitance.
Loop diuretics are used as an adjunct to saline to treat this condition.
hypercalcemia.
What is the most efficacious agent to treat exercise induced pulmonary hemorrhage?
furosemide.
Why do you not use aminoglycosides with loop diuretics?
because of ototoxicity
What is the most serious adverse effect of loop diuretics?
hypokalemia.
What is the most important adverse effect of using loop diuretics on diabetic patients?
hyperglycemia
Why don’t thiazide diuretics help in acute renal failure?
because they do not reach the site of action.
Where do thiazide diuretics act?
on the early distal tubules
T/F: thiazide diuretics have both oral and injectable forms.
False. only oral.
What is the main mechanism of action of thiazide diuretics?
they inhibit the Na+/Cl- symporter in the early distal convoluted tubules resulting in inhibition of reabsorption of Na+, Cl-, and diuresis.
What diuretics can be used to prevent kidney stones (uroliths)?
thiazide diuretics.
With which diuretics is the electrolyte imbalance more severe, thiazide or loop diuretics?
loop diuretics
T/F: thiazide diuretics can be used to treat localized or generalized edema of CHF.
True.
When are thiazide diuretics contraindicated?
in patients with hypercalcemia.
Where do potassium sparing diuretics act?
on the late distal tubule and collecting duct.
What other uses are there for potassium-sparing diuretics?
treatment of hypokalemia
Which potassium sparing diuretic is a steroid hormone?
Spironolactone.
What is the mechanism of action of spironolactone?
it competitively blocks aldoserone binding to the aldosterone-receptor in the late distal tubule and collecting duct. This results in excretion of NaCl and diuresis, as well as retention of K+ and H+.
What are one of the adverse effects of spironolactone?
Can cause systemic acidosis due to H+ retention.
T/F: spironolactone is not suitable for emergency use.
True. It takes about a day or 2 to take effect.
Why is the diuretic efficacy of spironolactone mild?
Because only 2% of Na+ reabsorption occurs in the late distal tubule and collecting duct.
What are the 2 theraputic uses of spironolactone?
diuretic and tx of primary and secondary hyperaldosteronism.
What is the mechanism of action of triamterene and amiloride?
they block epithelial Na+ channels in the luminal membrane of the principal cells in the late distal tubule and collecting duct. This results in the excretion ofNa+ and diuresis, as well as retention fo K+ and H+
What are the therapeutic uses of triamterene and amiloride?
tx of hypokalemia and hypomagnesemia.
T/F: triamterene is metabolized by the liver, resulting in an active metabolite.
True
Which carbonic anhydrase inhibitor is used to control mountain sickness?
acetazolamide
Which 2 carbonic anhydrase inhibitors are more likely to cause systemic acidosis?
acetazolamide and methazolamide
What carbonic anhydrase inhibitor is used to treat for onpen angle glaucoma and is good for the long term management of glaucoma?
dorzolamide and brinzolamide
What is the MOA for CAIs?
They reversibly inhibit CA at the proximal tubules (primary) and at the collecting ducts (secondary). This inhibits the exchange of H+ for Na.
How do CAIs affect intraocular pressure?
They lower intraocular pressure by unhibiting carbonic anhydrase in the eye, decreasing the formation of aqueous humor.
How are dorzolamide and brinzolamide administered?
Topically on the eye.
What is the drug of choice to treat central diabetes insipidus?
desmopressin.
What is the drug of choice to treat nephrogenic diabetes insipidus?
thiazide diuretics
What is the difference between central diabetes insipidus and nephrogenic diabetes insipidus?
central diabetes insipidus completely lacks ADH.
How can you diagnose whether a patient is suffering from central diabetes insipidus vs. nephrogenic diabetes insipidus?
Using ADH. If you see improvement, it is central.
