Diuretics Flashcards
Explain the main function of diuretics
They increase the kidney’s output of urine
Goal: lower BP and/or decrease edema
List the first 2 types of diuretics & their sites of action in the nephron
- Carbonic anhydrase inhibitors
Site: PCT (65-70% Na is absorbed) - Loop diuretic
Site: TAL or thick ascending limb of nephron loop (25% Na is absorbed)
List the next 2 types of diuretics & their sites of action in the nephron
- Thiazides
Site: DCT (5% Na is absorbed) - K-sparing diuretics
Site: collecting duct (1-5% Na is absorbed)
Recall which of the 4 diuretics is the most potent
loop diuretic (because it acts on TAL)
Explain the MOA of loop diuretics
Blocks reabsorption of Na, Cl, and K in TAL of nephron loop
Name a commonly used loop diuretic
Furosemide (Lasix)
Indications for loop diuretics
Used when critical fluid removal is necessary
- pulmonary edema
- renal failure (loop diuretic is effective even with low GFR!!)
- CHF
Name an adverse side effect to monitor closely when using loop diuretics
dehydration
List signs and symptoms of dehydration
- dry mouth
- excessive thirst
- oliguria (small amount of urine)
- dark urine
What is the medical consequences of dehydration
Severe dehydration can lead to hypovolemia and shock.
This also puts the patient at risk to develop clots.
Recall which electrolytes may be depleted with the use of loop diuretics
Potassium
***Digoxin + Furosemide has a potential problem! Lasix can cause hypokalemia, which puts patients at risk of digoxin toxicity –> monitor K level closely!
Describe a strategy to reduce the risk of ototoxicity with intravenous (IV) administration of loop diuretics
Do IV push very slowly!
What are other (minor) adverse effects of loop diuretics
Hyperglycemia
Hyperuricemia
High LDL level
Low Mg (muscle weakness, tremors, dysrhythmias)
Low Ca (teatny)
List 3 other examples of loop diuretics
Bumetanide
Torsemide
Ethacrynic acid
Thiazide diuretics: similarities to loop diuretics
Increase the renal excretion of Na, Cl, K, and water
Also elevate plasma glucose & uric acid
Thiazide diuretics: differences from loop diuretics
Thiazides are not effective when GFR is low
Identify the most commonly prescribed thiazide medication
Hydrochlorothiazide (Microzide)
Advise a patient on the best time of day to take a thiazide medication
Take it in the morning!
Thiazide increase urine output 2 hours after oral dose & lasts up to 12 hours.
List potential side effects of thiazides
Same as loop diuretics except for ototoxicity
electrolyte imbalances
dehydration/hypotension
Elevated glu, uric acid, and cholesterol
2 drugs interactions that you should be careful when administering thiazide
Same as loop diuretics
- digoxin toxicity
- lithium toxicity
Describe the function of K-sparing diuretics and how they are prescribed
K-sparing diuretics cause the mildest increase in urine output
Not often used in monotherapy, used with loop diuretics to counteract K loss
Name the 2 types of potassium-sparing diuretics
- Aldosterone antagonists: spironolactone (decrease serum Na, increase serum K)
- Non-aldosterone antagonists: triamterene & amiloride
Explain how mannitol increases urine output
Mannitol does not get reabsorbed and stay in nephron –> creates osmotic pressure and causes increased water diuresis
Recall the route of mannitol administration
IV
List the indications for mannitol use
- increased intracranial pressure (ICP)
- Elevated intraocular pressure
- low output acute renal failure
Describe the potential side effects of mannitol
Mannitol causes fluid to move from inside the cells into the intravascular space
–> be careful with patients with CHF and pulmonary edema (they are already fluid overload)
