DIURETICS: OSMOTIC DIURETICS & CARBONIC ANHYDRASE INHIBITORS

Prototype osmotic diuretic drug

Mannitol

Three primary clinical indications for Mannitol therapy

1. Decreasing intracranial pressure (ICP / cerebral edema). 2. Decreasing intraocular pressure (IOP / acute glaucoma). 3. Promoting excretion of toxic substances to protect kidneys during chemotherapy (e.g., cisplatin).

Physical mechanism by which Mannitol increases urine output

Increases the osmolality of renal tubular fluid, acting as an osmotic magnet that prevents water reabsorption in the proximal tubule and loop of Henle.

Primary emergency setting for Mannitol administration

Emergency clinical situations involving acutely elevated intracranial pressure (ICP) or intraocular pressure (IOP).

Reason Mannitol is contraindicated or used with extreme caution in heart failure

Causes a rapid fluid shift from tissues into the vascular space, which can overload the circulatory system and precipitate acute pulmonary edema.

Physical change that occurs to a Mannitol solution when exposed to low temperatures

Crystallization inside the vial or IV bag.

Nursing actions required when crystals are observed in a Mannitol solution

Warm the vial to completely dissolve all crystals, inspect for clarity, and administer using an in-line IV filter (never infuse if crystals remain).

Mannitol route of administration and diuresis onset time

Administered intravenously (IV); diuresis occurs within 1 to 3 hours.

Classification of Mannitol regarding potassium balance (wasting vs. sparing)

Potassium-wasting (increases the urinary excretion of sodium, chloride, water, and potassium).

Primary side effects and adverse reactions of Mannitol

Fluid and electrolyte imbalances, pulmonary edema, tachycardia, nausea and vomiting, and metabolic acidosis.

Prototype carbonic anhydrase inhibitor drug

Acetazolamide (Diamox)

Site of action along the nephron for carbonic anhydrase inhibitors

Proximal convoluted tubule

Specific enzymatic mechanism of Acetazolamide

Inhibits the enzyme carbonic anhydrase, preventing the reabsorption of sodium, potassium, and bicarbonate.

Three primary ions excreted in increased amounts due to carbonic anhydrase inhibitors

Sodium, potassium, and bicarbonate

Acid-base imbalance resulting from prolonged use of carbonic anhydrase inhibitors

Metabolic acidosis (caused by excessive urinary bicarbonate loss)

Primary clinical indication for carbonic anhydrase inhibitors

Decreasing intraocular pressure (IOP) in patients with open-angle (chronic) glaucoma

Two non-cardiac, non-renal off-label uses for Acetazolamide

1. Treatment and prevention of high-altitude sickness. 2. Management of epilepsy and seizures.

Renal complication caused by highly alkaline urine during Acetazolamide therapy

Crystalluria (formation of crystals and stones in the urinary tract)

Reason Acetazolamide can trigger hemolytic anemia in susceptible individuals

It is a sulfonamide derivative, which can precipitate red blood cell destruction (hemolysis) in sensitive patients.

Classification of Acetazolamide regarding potassium balance (wasting vs. sparing)

Potassium-wasting (increases urinary potassium excretion)