Diuretic agents Flashcards
Loop diuretics:
- Mechanism of action
- Administration
- Examples [3]
Mechanism:
- Inhibits NKCC2 co-transporter on the ASCENDING loop of Henle
- Increases delivery of Na+ to distal tubule, promoting natriuresis.
Administration:
- Oral
- IV
- IM
Examples:
- Furosemide
- Bumetanide
- Torasemide
Indications for Loop diuretics- like furosemide
- Acute pulmonary oedema
- Chronic heart failure
- Liver cirrhosis
- Resistant hypertension
- Nephrotic syndrome
- Acute renal failure
Unwanted effects of loop diuretics
Dehydration
Hypokalemia
- potentiates the effects of cardiac glycosides.
Deafness- when used with aminoglycoside antibiotics
Osmotic diuretics:
- Mechanism of action
- Example
Mechanism:
- Acts on the proximal tubule and the descending loop of Henle.
- Inhibits the reabsorption of water and Na+
Example:
- Mannitol
Indications for osmotic diuretics [4]
Cerebral oedema
Reduces intracranial pressure in glaucoma
Elimination of toxins via osmotic diarrhea
Acute renal failure
Unwanted effects of osmotic diuretics
Increases plasma volume by exerting osmotic pressure
- Cannot be used for hypertension
Kaliuretics
Diuretics that promote K+ excretion.
Natriuretics
Diuretics that promote Na+ excretion.
Aquaretics
Diuretics that promote water excretion without Na+ excretion.
Carbonic anhydrase inhibitors:
- Mechanism of action
- Example
Mechanism:
- Acts on proximal tubule
- Blocks H2CO3 formation, prevents Na+ and HCO3- reabsorption.
- Prevents Na+ being exchanged for H+, formed from carbonic acid.
Example:
Acetazolamide [Diamox]
Carbonic anhydrase inhibitor indications
Reducing intraoccular pressure in glaucoma
Decrease volume and pressure of CSF in epilepsy.
Unwanted effects of carbonic anhydrase inhibitors
Metabolic acidosis
Increased production of renal stone
Potassium sparing diuretics:
- Mechanism of action
- Examples [4]
Mechanism:
- Acts on distal tubule
- Competitively antagonises aldosterone.
- This inhibits the increased production of Na+ channels, reducing Na+ reabsorption.
- Affects protein synthesis—-> takes days to work.
Examples:
- Spironolactone
- Eplerenone
- Triamterene
- Amiloride
Indications of K+ sparing diuretics
Heart failure
Oedema
Unwanted effects of K+ sparing diuretics
Hyperkalemia- does not increase secretion of K+
Metabolic acidosis
GI upsets
Gynaecomastia
Menstrual
Testicular atrophy
Amiloride and triamterene
Potassium sparing diuretics
Physically blocks apical Na+ channels instead of antagonising aldosterone like other K+ sparing drugs.
Combining diuretic agents
Used to:
Increases diuretic effects
Avoid hypokalemia
- Loop/thiazide combined with K+ sparing
- Loop/thiazide given with K+ solution.
- Use diuretics containing K+
Thiazide diuretics:
- Mechanism of action
- Examples [2]
Mechanism:
- Acts on distal tubule
- Inhibits Na+/Cl- co-transporter
- Blocks Na+ absorption on apical membrane= natriuresis
Examples:
- Bendroflumethiazide
- Hydrochlorothiazide
Indications for thiazide diuretics
Hypertension
Oedema
Mild heart failure
Unwanted effects of thiazide diuretics [6]
Hypokalemia
Metabolic alkalosis:
- More stress placed on Na+/H+ exchanger to absorb Na+
- Promotes H+ loss
Increase in Uric acid= gout
Hyperglycaemia due to increased Ca2+ absorption
Hypercholesterolemia
Male impotence
Thiazie-like diuretics
- Mechanism
- Examples [4]
Like thiazide diuretics but with a different molecular structure.
- Inhibits Na+/Cl- co-transporter
Examples:
- Indapamide
- Benzthiazide
- Metolazone
- Xipamide
Xanthines
Chemical found in caffeine, theobromine, used as bronchodilator.
Acts as a weak diuretic- possible due to dilation of afferent arteriole.
ADH antagonists
Potential diuretics
- Prevents ADH making collecting duct impermeable to water, increasing aquaresis
Examples: Lithium Demeclocycline Amphotericin B Tolvaptan
These examples are either toxic or not that effective
Effectiveness of diuretics
Loop diuretics are the most effective:
Loop> Thiazide > Potassium sparing
Lasilactone
Furosemide + spironolactone
Co-amilofruse
Furosemide + amiloride
Co-flumactone
Hydroflumethiazide + spironolactone
Co-amilozide
Hydrocholrothiazide + amiloride