Diuretics Flashcards
Your patient is starting on a potassium-sparing diuretic and is worried about side effects. What do you tell him?
Side effects include hyperkalemia (leading to arrhythmias) and endocrine effects with spironolactone (gynecomastia and antiandrogen effects)
____ (Loop/Thiazide) diuretics increase calcium excretion; ____ (loop/thiazide) diuretics decreases it.
Loop; thiazide
What mechanism underlies volume contraction alkalosis?
Volume contraction increases angiotensin II activity, increasing proximal tubule H+/Na+ exchange and HCO3- reabsorption
Where does parathyroid hormone increase calcium reabsorption in the nephron?
Distal convoluted tubule
A patient of yours with a history of gout and diabetes wants to start hydrochlorothiazide for hypertension. You refuse. Why?
Hydrochlorothiazide increases levels of both uric acid and glucose, which may worsen the patient’s gout and diabetes, respectively
Fill in the blanks (thiazides/K+-sparing diuretics/loop diuretics/acetazolamide): ___ and ___ raise blood pH; ___ and ___ lower blood pH.
Loop diuretics and thiazides raise blood pH; acetazolamide and K+-sparing diuretics lower blood pH
What are three (general) clinical uses for loop diuretics?
To treat edematous states (congestive heart failure, cirrhosis, nephrotic syndrome, pulmonary edema), hypertension, and hypercalcemia
A patient starts a potassium-sparing diuretic. What are the main electrolytes absorbed and secreted at the site where this drug acts?
Potassium-sparing diuretics act on the collecting tubule, where NaCl (reabsorbed), K+ (secreted), and H+ (secreted) are exchanged
A patient taking torsemide is noted to have dilated renal afferent arterioles. This effect is blocked by NSAIDs. What is happening?
Torsemide, a loop diuretic, dilates the afferent arterioles by stimulating prostaglandin E (PGE) release, an effect inhibited by NSAIDs
A patient starts taking acetazolamide for mild altitude sickness. What is the mechanism of action of this drug?
It acts as a carbonic anhydrase inhibitor, causing self-limited sodium bicarbonate diuresis and a reduction in total-body bicarbonate stores
A patient takes mannitol. On which segments of the nephron does an osmotic agent such as mannitol exert its diuretic effects?
Proximal straight tubule and the thin descending loop of Henle
A patient takes a diuretic for increased intracranial pressure. What is the drug and its mechanism of action?
Mannitol, an osmotic diuretic, which increases tubular fluid osmolarity and therefore urine flow rate (also acts on intraocular pressure)
A patient of yours starts chlorthalidone for hypertension and notes fewer kidney stone attacks. Why might this be happening?
Hydrochlorothiazide increases DCT reabsorption of calcium, which reduces the likelihood of calcium-containing stones in the urine
In a patient on diuretics, labs show a high urine sodium and a low serum sodium. Can you pinpoint which diuretic(s) may be responsible?
Except for acetazolamide, no (all diuretics can cause this effect, so this is a nonspecific finding)
A patient on a loop diuretic is noted to have elevated calcium in his urine. Is the loop diuretic responsible?
Yes; loop diuretics decrease paracellular Ca2+ reabsorption, leading to increased urinary Ca2+ levels and hypocalcemia
What is the mechanism by which potassium-sparing diuretics cause acidemia?
Hyperkalemia leads to potassium entering all cells via the H+/K+ exchanger in exchange for H+ exiting cells
A patient with SIADH is given ADH antagonists for severe hyponatremia. Where do these act, and what do they block from being reabsorbed?
ADH antagonists act on the collecting duct, blocking the ADH-mediated reuptake of water
In the nephron, a site where only water is reabsorbed (without other electrolytes) is at the ____.
Thin descending limb of the loop of Henle
By what mechanism involving all cells does potassium loss lead to alkalemia?
K+ exits all cells (to maintain a normal serum level) in exchange for H+ entering cells (causing the alkalemia)
A man receives loop diuretics for a heart failure flare. How permeable to water is the site where they act? Are electrolytes absorbed there?
They act on the thick ascending loop of Henle, which is impermeable to water; yes (Mg2+, Ca2+, and Cl- are absorbed there)
A patient begins taking a second diuretic to offset the effect of furosemide. What part of the nephron does this second diuretic act upon?
The cortical collecting tubule (this is likely a potassium-sparing diuretic)
What is the mechanism of action of loop diuretics?
They block Na+/K+/Cl- thick ascending limb cotransporters, abolish medullary hypertonicity, and prevent urine concentration
A patient with a sulfa allergy needs urgent loop diuretic diuresis due to heart failure. What medication can you offer him?
Ethacrynic acid (it is a phenoxyacetic acid derivative, not a sulfonamide)
What are the mechanisms of action of spironolactone and eplerenone? What about triamterene and amiloride?
Spironolactone and eplerenone competitively antagonize the aldosterone receptor; triamterene and amiloride block luminal sodium channels
A patient starts a thiazide diuretic for hypertension. This acts at the same site as which prominent hormone?
Thiazide diuretics act on the distal convoluted tubule, where PTH acts to moderate Ca2+ absorption
A patient on a carbonic anhydrase inhibitor develops acidemia. What is the likely cause?
Acetazolamide causes the kidney to excrete more HCO3-, decreasing the body’s pH and leading to acidemia
Calcium excretion is increased by ____ (loop diuretics/thiazides) and decreased by ____ (loop diuretics/thiazides).
Loop diuretics (decreased paracellular reabsorption ); thiazides (enhanced paracellular reabsorption in proximal tubule and loop of Henle)
Name some clinical indications for acetazolamide.
Glaucoma, urinary alkalinization, metabolic alkalosis, altitude sickness, pseudotumor cerebri
A patient with anuria presents with heart failure. Is it safe to give this patient an osmotic diuretic?
No (osmotic diuretics such as mannitol are contraindicated in patients with anuria and/or heart failure)
What is the effect of the loop diuretic furosemide on calcium handling in the kidney nephron?
Furosemide increases calcium excretion (Loops Lose calcium)
Potassium and hydrogen secretion occurs at the ____ (cortical/medullary/both cortical and medullary) collecting tubule of the nephron.
Both cortical and medullary
Name at least two toxicities associated with acetazolamide.
Hyperchloremic metabolic acidosis (ACIDazolamide causes ACIDosis), paresthesias, ammonia toxicity, sulfa allergic reactions
Name some clinical uses of thiazide diuretics.
To treat hypertension, congestive heart failure, idiopathic hypercalciuria, nephrogenic diabetes insipidus
Serum levels of which substances are increased as a result of the effects of thiazide diuretics?
Glucose (hyperGlycemia), lipids (hyperLipidemia), uric acid (hyperUricemia), and calcium (hyperCalcemia) (hyperGLUC)
Both calcium and magnesium are reabsorbed primarily in the renal ____ (cortex/outer medulla/inner medulla).
Cortex
Name some clinical uses of potassium-sparing diuretics.
To treat hyperaldosteronism, potassium depletion, congestive heart failure
A patient takes acetazolamide for altitude sickness. What are the main electrolytes absorbed at the site where this drug acts?
It acts on the proximal convoluted tubule, where NaCl and NaHCO3-
How does a low potassium state lead to alkalemia and a paradoxical aciduria?
H+ rather than K+ is exchanged for Na+ at the cortical collecting tubule
Ethacrynic acid (a phenoxyacetic acid derivative) is an alternative to ____ for patients who suffer from ____. Name one toxicity.
Loop diuretics (furosemide, bumetanide, torsemide); sulfa allergies; hyperuricemia (never use ethacrynic acid to treat gout)
Name at least four toxicities associated with using loop diuretics.
Ototoxicity, Hypokalemia, Dehydration, Allergy (sulfa), Nephritis (interstitial), Gout (OH DANG!)
What acid-base abnormality is associated with thiazide diuretic use?
Hypokalemic metabolic alkalosis
A patient is noted to have low serum potassium and high levels of potassium in the urine. Could a diuretic be responsible?
Yes (all except the potassium-sparing diuretics can cause these findings)
