Diruetics Flashcards
What is the role of the kidney in salt water homeostasis?
regulate ECF volume and [ions] in the body
filter, excrete, reabsorbs necessary amount to keep body levels adequate
What are the major clinical indications for diuretic drug therapy?
Edema- generalized/local
Hypertension- essential, renal, aldosteronism
other- Hypo/Hypercalcemia, Urolithiasis, Glaucoma, Drug/Mineral toxicosis, metabolic acid/alkalosis, nephrogenic Disorders
What are the major classes of diuretic drugs?
Osmotic diuretics Loop diuretics Thiazides K sparing diuretics CA inhibitors Xanthines Urinary Acidifiers
What is the mechanism of Osmotic Diuretics?
they are filtered into the nephron at the glomerulus, but cannot be reabsorbed
thus increase osmotic pull, preventing water and ion re-absorption
leading to diuresis
What is mannitol? What is it used for?
Osmotic Diuretic
increases PG, increasing medullary blood flow
effective for acute management of cerebral edema
What are the therapeutic uses of Mannitol?
cerebral edema- reduces intracranial pressure
acute glaucoma- reduces intraocular pressure
Renal Failure- increases GFR volume, maintains urine flow,
Tx of ischemia/nephrotoxin induced acute tubular necrosis
Poison elimination
What are the adverse effects of Mannitol?
contraindicated in animals w/ generalized/acute pulmonary edema
not recommended in animals with cerebral hemorrhage, will enter the brain and cause increased fluid accumulation and increased intracranial pressure
What is the mechanism of action of Loop Diuretics?
reduce ion re-absorption via inhibition of Na/K/2Cl- co-transporter in the luminal membrane of the the thick ascending loop of henley
inhibit Ca2+ and Mg2+ re-absorption due to change in electrical gradient (luminal positive potential)
What is the most common loop diuretic?
Furosemide (Lasix)
others are: Torsemide, Bumetidine, and Ethacrynic Acid (not used in SA)
What are the therapeutic uses of Furosemide?
edema- rapid mobilization, very effective for pulmonary edema
chronic heart failure- best class to use
Acute renal failure- use in combo w/ mannitol
hypercalcemia- increases urinary Ca2+ secretion in dog/cat (tx for Vit D toxicosis)
EIPH in Race horses
HyperK if Mannitol ineffective
Tx of ascites- combo w/ other drugs
Antihypertensive
Tx post-parturient udder edema- approved drug
What are the adverse effects of Furosemide?
fluid-electrolyte imbalance, especially hypoK/Cl-
ototoxicity- deafness due to above imbalance in the endolymph of inner ear
Dehydration, metabolic alkalosis, hyperuremia (Gout), hypocalcemia, muscle weakness, CNS depression
Does Furosemide interact w/ other drugs? Which ones?
increased ototoxicty/nephrotoxicity w/ aminoglycosides/cisplatin
NSAIDS reduce diuretic response of loop drugs
increased hypoK during cocontaminant tx w/ corticosteroids/amphotericin B
may alter requirements of insulin/other anti-diabetic drugs
When is furosemide/other loop diuretics contraindicated?
patients w/ anuria, renal failure, hepatic dysfunction, and diabetes
What is the mechanism of action of Thiazides?
inhibition of Na+/Cl- symporter in the distal collecting tubule
increase the re-absorption of Ca2+ due to stimulation of Na+/Ca2+ antiporter
What are the 4 thiazide drugs?
Chlorothiazide
Hydrochlorothiazide
Trichlormethiazide
CHlorthalidone
What are the therapeutic usesnof thiazides?
long term diuretic therapy- adjunct tx in dogs and cats w/ CHF, animals with resistance to furosemide
Tx of systemic hypertension
tx of post parturient udder edema- approved
Nephrogenic DI in combo w indomethican leads to reduced urine output in dogs w/ DI
Ca-oxalate crystal uroliths- decreases these stones in dogs
What are the adverse effects of thiazides?
fluid-electrolyte imbalance
hypoK, gout, hyperCa w/ prolonged use
hyperglycemia/glucosuria- inhibition of proinsulin and insulin
Similar drug interaction as loop drugs
What is the mechansim of action of K+ sparing drugs?
Na+ channel blockers, reduce luminal potential and the driving force for K secretion leads to decrease in K+ secretion
reduction in lumen negative potential decreases H+ secretion in intercalated cells
NET RESULT (of filtrate) increase Na, Decreased K, Decreased H
What are the K sparing drugs?
Trimaterene and Amiloride
What is the mech of action of Aldosterone Antagonists?
competively bind aldosterone receptor, reducing the synthesis of aldosterone-induced proteins, inhibting their fx
Basically- inhibit Na/K channels, Na/K ATPase, Mitochondrial ATP pdx
Leads to a net result is same as K sparing
increase Na, Decreased K, Decreased H
What are the aldosterone antagonists?
Spironolactone and Potassium canrenoate
What are the therapeutic uses of aldosterone antagonists?
**used in conjunction w/ loop/thiazides
chronic tx of CHF
primary/secondary aldosteronism
tx of ascites
What are the adverse effects of aldosterone antagonists?
hyperK
metabolic acidosis
What are the CA inhibitors?
Carbonic Anhydrase inhibitors
reduce the # of H+ ions available for NA/K exchange
results in increased Bicarb, K+ excretion, and Cl- retention
leads to hyperchloremic acidosis
