Diuretics Flashcards
What are the most common uses for diuretics
Edema
Hypertension
Congestive Heart Failure


Primary site of action of carbonic anhydrase inhibitors
Within the proximal tubule
Carbonic anhydrase examples
Acetozolamide (Diamox)
Methazolamide (Neptazane).
Use of CA inhibitors
Used for glaucoma and As a prophylactic for Acute mountain sickness
Side effects of CA inhibitors
Hyperchloremic Metabolic Acidosis
Renal Stones (increased pH in lumen causes Ca+2 to ppt out of sol’n)
Renal Potassium Wasting - hypokalemia (increased Na+ in lumen causes K+ excretion via a Na+/K+ antiporter in the collecting duct
Site of action of osmotic diuretics
proximal tubule and thin descending and ascending limbs of the loop of Henle
Osmotic diuretic example
Mannitol (Osmitrol)
MOA of osmotic diuretics
- Produce an osmotic gradient and pull water into the lumen from surrounding tissues
- prevent reabsorption of water and solutes
Osmotic diuretics expand the extracellular fluid volume by pulling water from intracellular compartments. Thus, they decrease the viscosity of blood and prevent release of renin. One important thing to remember is that the above effects on expanded extracellular volume, decreased blood viscosity and less renin release is that the renal blood flow is increased, which results in more NaCl removal from the renal medulla. Reduces water and NaCl reabsorption
When should osmotic diuretics not be used
Should not be used in patients with peripheral edema
Can cause pulmonary edema in patients with heart failure or pulmonary congestion
Contraindicated in patients with active cranial bleeding
When are osmotic diuretics most useful
- Can reduce intracranial pressure, cerebral edema, can be used before and after neurosurgery
- They can be used to reduce intraocular pressure short term for acute glaucoma and pre- and post- ocular surgery
Side effects of osmotic diuretics
convulsions, thrombophlebitis, severe dehydration, headaches, chest pains, tachycardia, blurred vision, fever, chills
Loop diuretics site of action
Thick ascending limb
Examples of loop diuretics
Bumetanide (Bumex)
Furosemide (Lasix)
Torsemide (Demedex)
Loop diuretics MOA
Inhibit the Na+-K+-2Cl- symporter on the apical membrane of the thick ascending limb epithelial cells
Loop side effects
Hypokalemic metabolic alkalosis
Ototoxicity (NKCC2 transporter in ear)
Hyperuricemia, gout attacks (hypovolemia increases reabsorption of uric acid)
Hypomagnesemia- inhibiting Na+-K+-2Cl- symporter impacts potential difference across membrane which prevents Mg+2 reabsorption
Allergic reactions
Interference with calcium reabsorption
Kidney stones are concern with loop diuretics
When to use loop diuretics
They work very well and quickly at diuresis so they are often used when the GFR is low
acute pulmonary edema and other edematous conditions
- acute hypercalcemia: enhance Ca+2 excretion
- hyperkalemia- loop diuretics can significantly enhance urinary excretion of K+ , which is enhanced by simultaneous administration of NaCl
-acute renal failure- increased rate of urine flow and enhancement of K+ excretion is thought to be helpful
-anion disease: for treatment of toxic ingestions of bromide, fluoride, and iodide (normally reabsorbed in the thick ascending limb)
Contraindication of loop diuretics
Patients with sensitivities to sulfonamides
Thiazide diuretics MOA
Major - Distal convoluted tubule
Minor - Carbonic Anhydrase in the proximal tubule
Examples of thiazide diuretics
Hydrochlorothiazide (Esidrix, HydroDIURIL)
Chlorothiazide (Diuril)
Trichloromethiazide (Metahydrin)
Metolazone (Mykrox, Zaroxolyn)
Diuretics that shouldnt be taken with NSAIDs
Loops, thiazides
Thiazides MOA
- inhibit Na/Cl symporter from the luminal side of the distal convoluted tubule
- enhance Ca+2 reabsorption in the DCT because the Na/Ca exchanger is more active (low Na inside cell)
secreted by the organic acid secretory system in the proximal tubule to the lumen and compete with secretion of uric acid, elevate serum uric acid

Side effects of thiazides
As with loop diuretics, hypokalemic metabolic alkalosis, hyperuricemia
increased calcium reabsorption, can be used for kidney stones
Impaired carbohydrate tolerance
Hyperlipidemia
Hyponatremia
Allergic reactions
Contraindications of thiazides
Patients with hepatic cirrhosis, borderline renal failure, or acute heart failure
Thereapeutic uses of thiazides
edema associated with congestive heart failure, nephroticsyndrome, chronic renal failure, and glomerulonephritis (as long as GFR is >30-40 mL/min)
Since they decrease blood pressure in hypertensive patients, they are used alone or in combination with other antihypertensive drugs to treat hypertension
Since they reduce Ca+2 excretion, they can be used to treat Ca+2 nephrolithiasis or osteoporosis
They are used for treatment of diabetic nephropathy, but GFR must be above 30-40 mL/ min
What is unique about loop vs thiazide dosing
Loops have a rapid increase in efficacy with small changes in dosing. Thiazides plateau in efficacy

Site of action of K+ sparing diuretics
Collecting tubules
MOA of K+ sparing diuretics
Prevent K+ secretion by antagonizing the effects of aldosterone in the collecting tubules
Amiloride and Triamterene directly decrease the sodium channel activity without altering the mineralocorticoid receptor
Spinonolactone competitively inhibits the mineralocorticoid receptor
Examples of K+ sparing diuretics
Amiloride
Triamterene
Spironolactone
K+ sparing diuretics indications
Amiloride and Triamterene SPECICIFALLY INDICATED for treatment of polyuria and polydipsia due to lithium
Spironolactone SPECIFICALLY INDICATED in patients with primary aldosteronismor heart failure because blocking the mineralocorticoid receptor decreases the adverse effects of aldosterone on the heart.
-preferred in patients with cirrhosis
Side effects of K+ sparing diuretics
Amiloride is well tolerated, few side effects other than hyperkalemia
Triamterene is not as well tolerated as amiloride. It is potentially nephrotoxic and in half of patients leads to crystalluria and cast formation
Spironolactone may cause menstural abnormalities, gynecomastia, impotence, reduced libido
What diuretics can exacerbate gout
Loops, thiazides