diuretics

Question 1

what is diuresis

Answer 1

increased urine production

Question 2

what are the clinical indications

Answer 2

CHF, oliguric/anuric renal failure, cavity effusions, peripheral edema

Question 3

what are the 5 classes of diuretics

Answer 3

1. carbonic anhydrase inhibitors
2. osmotic diuretics
3. loop diuretics
4. thiazide diuretics
5. potassium sparing diuretics

Question 4

where is the site of action in loop diuretics

Answer 4

Na-K-Cl cotransport in ascending (thick) loop of henle

• block cotransport - decreased reabsorption of solutes - increased solutes in collecting ducts - decreased osmotic gradient - reduced reabsorption of H2O - increased urine production

Question 5

characteristics of loop diuretics

Answer 5

• active in tubular fluid
• highly protein bound not filtered at glomerulus
• absorbed from blood then secreted by PCT into tubular fluid
• secretion is renal blood flow dependent the lower the RBF the lower the loop diuretic in the tubular fluid
• patients with renal disease and dehydrated patients may need higher dosages

Question 6

what are the clinical characteristics of loop diuretics

Answer 6

• potent : dehydration (can be servere)
• electrolyte depletion, alkalinizing
• rapid onset
• variable bioavailability
• resistance
• ototoxicity
• azotemia, hyperkalemia, hypocalemia, hypomagnesemia

Question 7

what is loop diuretic resistance

Answer 7

• reduced absorption (intestinal edema)
• reduced GFR (renal failure, dehydration)
• changed in albumin
• need for increasing dosaged or combination therapy

Question 8

characteristics of furosemide

Answer 8

• rapid onset (IV: 5 min; PO < 60 min)
• duration of action (IV: 2-3 hrs; PO: 6hrs dog 12-24 hrs cat)
• oral bioavailability is variable within and across species
• prone to developing reistance

loop diuretic

Question 9

characteristics of torsemide

Answer 9

• 10x as potent as furosemide
• durationof action (once or twice daily oral)
• oral formulation well absorbed
• diuresis is more constant at dosages < 0.3 mg/kg (dog)
• less prone to resistance

loop diuretic

Question 10

what are thiazide diuretics

Answer 10

blocks Na - Cl cotransporter in DCT

• mild to moderate increases in urine volume
• potassium wasting
• ineffective with low RBF
• relative potency low in dogs and cats
• increase calcium reabsorption and result in hypercalcemia

Question 11

hydrochlorothiazide (HCTZ)

Answer 11

• thiazide diuretic
• small animal

Question 12

trichlormethiazide and dexamethasone

Answer 12

• thiazide diuretics
• naquasone bolus for bovine udder edema, equine limb edema

Question 13

what are potassium sparing diuretics

Answer 13

blocks aldosterone receptor

• increase Na excretion
• increased K retention
• inhibits RAAS: neuroendocrine modulator
• spirolactone may improve survival chronic CHF dogs
• potential cardioprotective/antifibrotic effects

Question 14

spironolactone

Answer 14

most commonly used postassium sparing diuretic

• mild diuretic effect
• add to loop diuretic if suspect resistance
• oral only
• peak diuresis 2-3 days

Question 15

what are osmotic diuretics

Answer 15

• increase H2O excretion
• indication: oliguric renal failure

Question 16

what is ARF-oliguric in osmotic diuretic

Answer 16

volume load

• kidney needs to be perfused in order to produce urine
• easy to volume overload if oliguric/anuric

mannitol

• test dose

furosemide

• high dose
• cri

furosemide plus dopamine