Diuretics Flashcards
metabolic acidosis as SE
Sulfanilamide
prototype drug
Acetazolamide
- limited usefulness as diuretics
CAIs
- forerunners of diuretics
CAIs
Zn metalloenzyme found in proximal tubular epithelial cells (where too??)
Carbonic Anhydrase
- Luminal and basolateral membranes (type IV)
- Cytoplasm (type III)
first to discover CA in mammalian kidneys
Davenport and Willhelmi (1941)
Key role in NaHCO3 reabsorption and acid secretion
Carbonic anhydrase
Inhibit the enzyme carbonic anhydrase, blocking NaHCO3 reabsorption in PCT
Carbonic anhydrase Inhibitors MOA
MOA of Carbonic Anhydrase Inhibitors
Inhibit the enzyme carbonic anhydrase, blocking NaHCO3 reabsorption in PCT
collecting duct as secondary site of action (blocking and secretion)
collecting duct as secondary site of action (blocking and secretion)
MOA of Carbonic Anhydrase Inhibitors
Extrarenal action of CAIs
Extrarenal actions:
- Decreases rate of formation of aqueous humor -> reduces IOP
- Frequently causes paresthesias and somnolence
- Anticonvulsant (acetazolamide)
- Increases CO2 levels in peripheral tissues; decreases CO2 levels in expired gas
- Reduce gastric acid secretion (large doses)
Decreases rate of formation of aqueous humor -> reduces IOP
CAIs
Frequently causes paresthesias and somnolence
CAIs
Anticonvulsant
acetazolamide
Increases CO2 levels in peripheral tissues; decreases CO2 levels in expired gas
CAIs
Reduce gastric acid secretion (large doses)
CAis
Dose Acetazolamide
125 mg half, 250 mg and quarter-scored tablets
1% ophthalmic suspension
Brinzolamide
2% ophthalmic suspension
Dorzolamide
primary indication is Glaucoma, no diuretic effect, no systemic effect and ↓IOP
Brinzolamide, Dorzolamide Topical agents
open-angle glaucoma
CAIs
CHF-associated and drug induced edema
acetazolamide
Epilepsy
(acetazolamide)
symptomatic relef and/or prophylaxis for acute mountain or altitude sickness
CAIs
*used nightly for 5 days before climbing to prevent weakness, breathlessness
familial periodic paralysis
CAIs
correction of metabolic alkalosis (diuretic-induced H+ excretion)
CAIs
bone marrow depression, skin toxicity, sulfonamide-like renal lesions, hypersensitivity reactions (SJS)
AE - CAIs
signs on bulla skin, deadly if on mucosa
SJS
drowsiness and paresthesias
AE - CAIs
Hepatic encephalopathy
AE - CAIs
( diversion of ammonia of renal origin from urine into the systemic circulation -> induce or worsen hepatic encephalopathy therefore drugs are contraindicated to patients with hepatic cirrhosis
AE - CAIs
Hepatic encephalopathy
calculus formation, ureteral colic
AE - CAIs
(owing to ppt of calcium phosphate salts in an alkaline urine)
AE - CAIs
Calculus formation, ureteral colic
worsening of metabolic or respiratory acidosis
AE - CAIs
Drugs are contraindicated in patients with hyperchloremic acidosis or severe COPD
AE - CAIs
worsening of metabolic or respiratory acidosis
Na+ and K+ wasting
AE - CAIs
CI for patients w/ Na+ or K+ depletion)
AE - CAIs
CI for patients w/ Na+ or K+ depletion)
- Most effective diuretics available
LOOP DIURETICS
- High-ceiling diuretics
LOOP DIURETICS
Highest efficacy in mobilizing Na+ and Cl- from the body
LOOP DIURETICS
*produce copious amounts of urine
LOOP DIURETICS
Act directly on the thick ascending limb of the loop of Henle to inhibit sodium and chloride reabsorption
LOOP DIURETICS
MOA of Loop diuretics
Act directly on the thick ascending limb of the loop of Henle to inhibit sodium and chloride reabsorption
Increase renal prostaglandins, resulting in the dilation of blood vessels and reduced peripheral vascular resistance (↑ renal blood flow)
LOOP DIURETICS
– impt role in mediating renin release reponse to loop diuretics
Prostacyclins
LOOP DIURETICS
Prostaglandins have a role in their diuretic action and NSAIDS like indomethacin that interfere in prostaglandin synthesis can reduce the diuretic action of these agents
LOOP DIURETICS
Decrease renal vascular resistance and increase renal blood flow
LOOP DIURETICS
Other actions of loop diuretics
- Increase renal prostaglandins, resulting in the dilation of blood vessels and reduced peripheral vascular resistance (↑ renal blood flow)
* Prostacyclin – impt role in mediating renin release reponse to loop diuretics
* Prostaglandins have a role in their diuretic action and NSAIDS like indomethacin that interfere in prostaglandin synthesis can reduce the diuretic action of these agents - Decrease renal vascular resistance and increase renal blood flow
Lasix dosage form
Tablet and ampule
– greater S/E therefore limited use (a loop diuretic)
Ethacrynic acid
more potent than furosemide , ↑ use
Bumetanide
DOC: acute pulmonary edema of HF
LOOP diuretics
given parenterally due to rapid action
Ind: Hypercalcemia (+hydration)
LOOP DIURETICS
Ind: - Hyperkalemia
LOOP DIURETICS
Ind: Hyponatremia
(+ hypertonic saline
LOOP DIURETICS
Ind: Acute renal failure
oliguric to nonoliguric
LOOP DIURETICS
Ind: - Forced diuresis in drug overdose
LOOP DIURETICS
Ind: Hypertension refractory to other diuretics or antihypertensives
LOOP DIURETICS
Administered orally or parenterally
LOOP DIURETICS
rapid onset of action (IV)
LOOP DIURETICS
duration of action is relatively brief (2 to 4 hrs)
LOOP DIURETICS
secreted into urine
LOOP DIURETICS
A/E Hypokalemia
TX?
Tx: Potassium-sparing diuretics or dietary supplementation with K+
LOOP DIURETICS
A/E Hypomagnesemia
(chronic use + low dietary intake of Mg 2+) = Elderly
LOOP DIURETICS
A/E Hyperuricemia
furosemide, ethacrynic acid compete with uric acid for the renal and biliary secretory systems, thus blocking its secretion and inturen causing or exacerbating gouty attacks)
LOOP DIURETICS
A/E Ototoxicity
(+aminoglycosides; rapid IV > PO)
*Tinnitus- hearing impairment deafness, vertigo, sense of fullness in the ears
*vestibular function too affected
LOOP DIURETICS
A/E - Sulfonamide-related hypersensitivity rxns
(Furosemide and Bumetanide)
LOOP DIURETICS
- synthesized to enhance potency of CAIs
Thiazides
- discovered to increase NaCl excretion
Thiazides
- Benzothiadiazine derivatives (chlorothiazide) are
Thiazides
- Most widely used diuretic drugs for tx of Hypertension
Thiazides
- Sulfonamide derivatives; related in structure to CAIs
- Significantly greater diuretic activity than acetazolamide
Thiazides
- Affect the distal convoluted tubule
Thiazides
- All have equal max diuretic effects, differing only in potency(expressed on a per-milligram basis) -> “ceiling diuretics”
*Even if increase dose of drug, it will not give ↑/enhance therapeutic action but only toxic actions
Thiazides
Act mainly in the cortical region of the ascending loop of Henle and the distal tubule to decrease the reabsorption of Na+, apparently by inhibition of a Na+/Cl- co-transporter on the luminal membrane of the tubules
Thiazides
- first modern diuretic that was active orally and was capable of affecting the severe edema of cirrhosis and heart failure w/ a min. of S/E
Chlorothiazide
- less ability to inhibit CA than chlorothiazide
Hydrochlorothiazide
- Newer derivative used more commonly
Hydrochlorothiazide
- more potent (required dose is considerably lower)
Hydrochlorothiazide
- efficacy is exactly the same as that of the parent drug
Hydrochlorothiazide
IND: - mainstay of antihypertensive medication
Thiazides
IND:- HF (when additional diuresis is needed)
Thiazides
IND:- Hypercalciuria
Thiazides
IND:- Nephrogenic diabetes insipidus (substitute for ADH)
Thiazides
- Effective orally
Thiazides
- Most thiazides take ___ wks to produce a stable reduction in BP
1 to 3 wks
- Exhibit a prolonged biologic half-life
Thiazides
- secreted by the organic acid secretory system of the kidney
Thiazides
A/E - Hypokalemia (↑common)
Thiazides
A/E - Hyponatremia
Thiazides
A/E - Hyperuricemia
- increase serum uric acid by decreasing the amt of acid excreted by the organic acid secretory system
Thiazides
A/E - Hypercalcemia
Thiazides
A/E - Hyperglycemia
- due to impaired release of inculin and tissue uptake of glucose
Thiazides
A/E - Hyperlipidemia
Thiazides
A/E - Volume depletion
Thiazides
A/E - Hypersensitivity rxns
Thiazides
- compounds that lack the thiazide structure but like thiazides they have the unsubstituted sulfonamide groups and share same MOA
Thiazide -like
- Non-thiazide derivatives that behaves like HCTZ
Chlorthalidone
- very long duration of action ; therefore, is often used to tx Hypertension
Chlorthalidone
- given 1/d for this in
Chlorthalidone
- more potent than thiazides
Metolazone
- causes Na+ excretion in advanced renal failure
Metolazone
- lipid-soluble, nonthiazide diuretic that has a long duration of action
Indapamide
- at low doses, shows significant antihypertensive action w/ min diuretic effects
Indapamide
- metabolized and excreted by the GIT and kidneys
Indapamide
- less likely to accumulate in patients w/ renal failure
Indapamide
- act in the collecting tubule to inhibit Na reabsorption and K+ excretion
Potassium-sparing diuretics/ Na-channel inhibitors
- Major use: Tx of hypertension, most often in combination w/ a thiazide
Potassium-sparing diuretics/ Na-channel inhibitors
- discontinue exogenous K supplementation
Potassium-sparing diuretics/ Na-channel inhibitors
- close monitory of serum K levels
Potassium-sparing diuretics/ Na-channel inhibitors
- avoided in patients with renal dysfunction because of increased risk of hyperkalemia
Potassium-sparing diuretics/ Na-channel inhibitors
- synthetic steroid that antagonizes aldosterone at intracellular cytoplasmic receptor sites
Spironolactone
- Inactive spironolactone-receptor complex (does not bind to DNA -> inhibition of protein synthesis)
Spironolactone
- mediator proteins not present to stimulate Na+/K+ exchange sites
Spironolactone
- Inhibition of Na+ reabsorption and K+/H+ secretion
Spironolactone
*in patients with no significant circulating levels of aldosterones, like with Addison disease (primary adrenal deficiency) , no diuretic effect of the drug occur
Spironolactone
(Spironolactone + HCTZ)
ALDAZIDE
- often given in conjunction w/ a thiazide or loop diuretic to prevent the K+ excretion
Aldosterone Antagonist
- diuretic of choice in patients with hepatic cirrhosis
Aldosterone Antagonist
- secondary hyperaldosteronism
Aldosterone Antagonist
- completely absorbed orally
Aldosterone Antagonist
- strongly bound to proteins
Aldosterone Antagonist
- rapidly converted to an active metabolite, canrenone (has mineralocorticoid-blocking activity)
Aldosterone Antagonist
- induces hepatic cytochrome P450
Aldosterone Antagonist
- Gastric upsets -> peptic ulcers
Aldosterone Antagonist
- Gynecomastia in male patients; menstrual irregularities in female patients (high doses on chronic use)
Aldosterone Antagonist
- Hyperkalemia, nausea, lethargy and mental confusion
Aldosterone Antagonist
- block Na+ transport channels, resulting in a decrease in Na+/K+ exchange
Triamterene and Amiloride
- ability to block the Na+/K+ - exchange site does not depend on the presence of aldosterone
Triamterene and Amiloride
- not very efficacious diuretics
Triamterene and Amiloride
- commonly used in combination with other diuretics usually for their potassium-sparing properties
Triamterene and Amiloride
- leg cramps
Triamterene and Amiloride
- possibility of increased blood urea nitrogen, uric acid and K+ retention
Triamterene and Amiloride
- agents that are freely filtered at the glomerulus, undergo limited reabsorption by the renal tubule, and are relatively inert pharmacologically
Osmotic diuretics
- administered in large enough doses to increase significantly osmolality of plasma and tubular fluid
Osmotic diuretics
- not useful for treating conditions in which Na retention occurs
Osmotic diuretics
Increase the osmotic pressure at the PCT and LOH to prevent water reabsorption
Osmotic diuretics
what about mannitol?
- IV only
- prolonged standing of mannitol (may ppt)
- subject to heat (glass bottles); shake bottles (agitate) until clear
- used to maintain urine flow following acute toxic ingestion of substances capable of producing acute renal failure
Osmotic diuretics
- mainstay treatment for patients with increased intracranial pressure or acute renal failure due to shock, drug toxicities and trauma
Osmotic diuretics
- extracellular water expansion
Osmotic diuretics
- dehydration
Osmotic diuretics
- hypo- or hypernatremia
Osmotic diuretics
*The expansion of extracellular water results because the presence of mannitol in the extracellular fluid extracts water from the cells and causes hyponatremia until diuresis occurs.
Osmotic diuretics