Diuretics (Thiazide, Loop, K-Sparing, Mannitol)

Cardiovascular

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Examples

hydrochlorothiazidefurosemidespironolactonemannitol

Prefix / Suffix: -thiazide, -semide (loops), -actone (K-sparing)

Physiology

Diuretics act on the kidneys to increase urine formation by affecting sodium and water reabsorption. This reduces blood volume, decreases preload, and lowers blood pressure.

Mechanism of Action

Thiazides inhibit sodium reabsorption in the distal tubule (moderate diuresis). Loop diuretics inhibit Na-K-Cl reabsorption in the loop of Henle (powerful diuresis). Potassium-sparing diuretics block aldosterone or sodium channels (mild diuresis with potassium retention). Osmotic diuretics (mannitol) pull water into the renal tubules by increasing osmotic pressure.

Indications

Hypertension (thiazides)
Edema in heart failure or renal disease (loops)
Hyperaldosteronism (potassium-sparing)
Increased intracranial pressure / cerebral edema (mannitol)
Acute kidney injury (mannitol)

Side Effects / Adverse Effects

Hypokalemia (thiazide, loop — due to potassium loss)
Hyperkalemia (potassium-sparing — due to potassium retention)
Dehydration (excess fluid loss)
Hypotension (reduced blood volume)
Ototoxicity (loop diuretics, especially high doses)
Hyperglycemia (thiazides affect glucose metabolism)
Mannitol: fluid overload, pulmonary edema (draws fluid into circulation before excretion)

Contraindications

Severe dehydration
Anuria
Severe electrolyte imbalance
Potassium-sparing: hyperkalemia
Mannitol: heart failure, pulmonary edema

Nursing Considerations

Monitor fluid balance and daily weight (detects fluid loss or retention early)
Check electrolyte levels regularly (risk of hypo- or hyperkalemia depending on type)
Monitor blood pressure (risk of hypotension due to volume depletion)
Give in the morning (prevents nocturia and sleep disturbance)
For loop diuretics: monitor hearing (risk of ototoxicity at high doses)
For potassium-sparing: avoid potassium supplements (prevents hyperkalemia)
For mannitol: monitor for signs of fluid overload like crackles or dyspnea (fluid shifts can worsen pulmonary edema)

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