Diuretics Flashcards
Loop diuretics
Loop diuretics are a class of medications that act on the Loop of Henle in the kidney to promote diuresis (increased urine production). They are the most potent diuretics and are commonly used to manage conditions involving fluid overload or edema.
Normal function of the thick ascending limb in the loop of henle
Sodium (Na⁺), Potassium (K⁺), and Chloride (Cl⁻) reabsorption: In the thick ascending limb, the Na⁺-K⁺-2Cl⁻ symporter (NKCC2 transporter) actively reabsorbs Na⁺, K⁺, and Cl⁻ ions from the filtrate into the tubular cells.
Water impermeability: The thick ascending limb is impermeable to water, so solute reabsorption decreases the osmolarity of the filtrate while increasing medullary interstitial osmolarity, which is critical for urine concentration.
loop diuretics mechanism of action
Loop diuretics act specifically on the thick ascending limb of the Loop of Henle, where they inhibit the Na⁺-K⁺-2Cl⁻ symporter (NKCC2 transporter)
1.Decreased sodium, potassium, and chloride reabsorption:
By blocking this transporter, these ions remain in the tubular fluid and are excreted in the urine.
2.Increased water excretion:
Water follows the retained sodium, leading to increased urine production (diuresis)
3.Disruption of the medullary concentration gradient:
Normally, the thick ascending limb helps create a hypertonic medullary environment critical for water reabsorption. Loop diuretics impair this gradient, reducing the kidney’s ability to concentrate urine
4.Increased excretion of calcium and magnesium:
The positive luminal charge, generated by potassium recycling, normally drives paracellular reabsorption of calcium and magnesium. Blocking NKCC2 disrupts this process, leading to calcium and magnesium loss.
clinical uses of loop diuretics to treat …
heart failure: To reduce edema and pulmonary congestion.
Edema from kidney or liver disease.
Acute pulmonary edema: Rapid relief of fluid overload in the lungs.
Hypertension: Particularly when associated with fluid retention.
Hyperkalemia and hypercalcemia: They promote potassium and calcium excretion.
Acute kidney injury (AKI): To stimulate urine flow (controversial use).
Common Loop Diuretics
furosemide (Lasix)- elimination is reduced by renal dsyfunction
Bumetanide
Torsemide- Greater potency and duration of action compared to Furosemide
Ethacrynic acid (used when sulfa allergy is present)
pharmacokinetics of loop diuretics
Most powerful diuretic
Causes up to 25% of the nephron filtrate to be voided as urine
Vasodilates
Good oral and IV absorption
Furosemide phase II liver metabolism
Action: Oral / 1 hr, IV / 30 mi.
Half life 90 minutes n
Duration of action 4-6 hours
nursing considerations with diuretics
Ensure IV administration by infusion pump for doses of +80 mg Furosemide (Lasix)
Pump rate should not exceed 4mg /minute
not to be diluted with glucose solutions
Bumetanide (Burinex)
2-5 mg IV over 30 -60 minutes
Rapid IV doses lead to toxicity
Tinitus
Circulatory collapse
Seizures
Monitor Potassium levels
Deafness (compounded by use of Aminoglycoside Antibiotics)
Electrolyte imbalance
thiazides
Thiazides act on the distal convoluted tubule of the nephron in the kidney.
They inhibit the Na⁺/Cl⁻ symporter, which reduces sodium and chloride reabsorption.
This leads to increased excretion of sodium, chloride, and water, along with potassium and hydrogen ions, resulting in a reduction of blood volume and blood pressure.
pharmacokinetics of thiazides
Similar absorption to loop diuretics. May have more effective oral absorption in oedema (bendrofluazide)
Maximum effect 4-6 hours
Duration of effect 8 -12 hours
May cause
vasodilation (as do loop diuretics) ? Indirect opening of vascular smooth muscle potassium Ion channels
Hyperglycemia:- Small and maybe insignificant change
thiazide and thiazide like drugs
Bendroflumethazide- Primary drug used for hypertension
Metolazone (thiazide like)- 70-95% secreted unchanged, Absorption reduces with increase in HF, although also preparation dependant , Causes diuresis when GFR < 20mL/min
Chlortalidone (thiazide like)- Long acting, Drug excreted largely unchanged (70-95%)
indications for use of thiazides
Hypertension (low doses (2.5 mg O.D.) cause maximal effect)
Mild HF (normally in association with loop diuretics)
Severe Resistant HF in association with loop diuretics
In prevention of renal stone formation
k sparing diuretrics
Potassium-sparing diuretics are a class of diuretics that help eliminate sodium and water from the body while retaining potassium. They are often used in combination with other diuretics (like thiazides or loop diuretics) to prevent hypokalemia (low potassium).
retain serum potassium and effect takes48 hrs for full onset
mechanisms of k sparing diuretic
Potassium-sparing diuretics work in the distal convoluted tubule and collecting duct of the nephron:
Aldosterone Antagonists:
Block the action of aldosterone, a hormone that promotes sodium reabsorption and potassium excretion.
Result: Sodium and water excretion, but potassium is retained.
Sodium Channel Blockers:
Directly inhibit sodium channels in the distal nephron.
Result: Sodium is excreted, and potassium excretion is reduced.
examples of potassium sparing diuretics
Spironolactone
Eplerenone
indications for potassium sparing diuretics
In patients where hypokalemia is exceptionally harmful (digoxin, amiodarone)
HF (improves survival)
Specialist Managed
Hyperaldosteronism (Conn’s syndrome)
