Diuretics Flashcards
What is the primary mechanism of diuretics?
Reduce sodium reabsorption in the nephron → increase Na⁺/water excretion
List the 5 classes of diuretics
Carbonic anhydrase inhibitors (Acetazolamide)
Thiazides (Bendroflumethiazide, Hydrochlorothiazide)
Loop diuretics (Frusemide, Bumetanide)
Potassium-sparing
Osmotic diuretics
Carbonic Anhydrase (CA) Inhibitors: Prototype drug & mechanism?
Acetazolamide → inhibits CA in PCT → ↓HCO₃⁻/Na⁺ reabsorption
Carbonic Anhydrase Inhibitors: Key clinical uses (non-diuretic)?
Glaucoma, mountain sickness, epilepsy
Carbonic Anhydrase Inhibitors: Major side effect?
Metabolic acidosis (contraindicated in CKD)
Thiazides: Prototype drugs?
Hydrochlorothiazide, Chlorthalidone (thiazide-like)
Thiazides: Main clinical use?
Hypertension (↓plasma volume & peripheral resistance)
Thiazides: Key side effects?
SEs of thiazides:
Hypokalemia, hyponatremia (elderly), hypercalcemia, hyperglycemia.
Loop Diuretics: Prototype drugs?
Furosemide, Bumetanide
Loop Diuretics: Mechanism & potency?
Block Na⁺/K⁺/2Cl⁻ in Loop of Henle → most potent diuresis.
Loop Diuretics: Clinical uses/indications?
Heart failure, CKD volume overload, hypertension.
Loop Diuretics: Key side effects?
Hypokalemia, dehydration (→ AKI), ototoxicity, CALCIUM BASED KIDNEY STONES
Potassium-Sparing Diuretics: Two subclasses & prototypes?
ENaC blockers: Amiloride, Triamterene.
Aldosterone antagonists: Spironolactone, Eplerenone.
Potassium-Sparing Diuretics: Key uses?
Heart failure, cirrhosis, hyperaldosteronism, hypokalemia (from other diuretics)
Potassium-Sparing Diuretics: Major risk?
Hyperkalemia (esp. with CKD/ACE inhibitors)
Osmotic Diuretics; Mannitol + MoA + SE
Mannitol MoA= Freely filtered, not reabsorbed → ↑tubular osmolarity → ↓water reabsorption
SE= fluid overload
Osmotic Diuretics: Clinical uses?
Cerebral edema, Oliguric acute kidney injury (AKI)
When to AVOID Diuretics; Major contraindications for each class?
All diuretics:
- Hypotension/dehydration (risk of shock/renal failure)
- Anuria (no urine output)
K⁺-sparing (spironolactone, amiloride):
- Hyperkalemia (will worsen it)
- CKD (especially if GFR <30)
CA inhibitors (acetazolamide):
- CKD (causes metabolic acidosis)
- Liver cirrhosis (risk of hepatic encephalopathy)
Loops/thiazides:
- Severe hypokalemia (will worsen it)
- Sulfa allergy (cross-reactivity with thiazides/furosemide)
SGLT2 Inhibitors (canagliflozin, dapagliflozin, empagliflozin, ertugliflozin) What are the renal benefits?
↓Hyperfiltration, ↓albuminuria, ↓GFR decline (cardioprotective)
Side effects of SGLT2 Inhibitors
Glycosuria → ↑genital mycotic infections
Best diuretic for…
- HTN
- Acute pulmonary oedema
- hyperaldosteronism
- cerebral oedema
HTN? → Thiazides
Acute pulmonary edema? → Loops
Hyperaldosteronism? → Spironolactone
Cerebral edema? → Mannitol
What are the critical side effects of each of the following diuretics:
- Loops
- Thiazides
- Spironolactone
- Acetazolamide
Loops → Hypokalemia, ototoxicity
Thiazides → Hyponatremia (elderly), hypercalcemia
Spironolactone → Hyperkalemia, gynecomastia
Acetazolamide → Metabolic acidosis
What is a sulfa allergy, and why does it matter for diuretics?
sulfa allergy= hypersensitivity to sulfonamide antibiotics (e.g., sulfamethoxazole).
Relevance to diuretics:
Cross-reactivity risk with sulfa-containing diuretics:
- Thiazides (HCTZ, chlorthalidone)
- Loop diuretics (furosemide, bumetanide)
Safe diuretics in sulfa allergy:
- K⁺-sparing (spironolactone, amiloride)
- Osmotic (mannitol)
- CA inhibitors (acetazolamide—weak sulfa link, but often tolerated)
Thiazide-like drugs
Chlorthalidone, Indapamide, Metolazone
