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Flashcards in Diuretics continued Deck (18)

Next are the Carbonic Anhydrase Inhibitors: Acetazolamide. What is the action of these inhibitors?

-Inhibit both extracellular and intracellular forms of carbonic anhydrase, resulting in reduction of HCO3 reabsorption in the proximal convoluted tubule


Inhibition of carbonic anhydrase is associated with a rapid rise in what?

Urinary HCO3 excretion
Development of a hypercholoremic metabolic acidosis


How is carbonic anhydrase inhibitor a mild diuretic?

H2CO3 provides the protons H required for the activity of the Na/H transporter, thus inhibition of the enzyme results in a reduction of Na reabsorption


How is a carbonic anhydrase inhibitor used in glaucoma?

--decreases the formation of aqueous humor and so decreases intraocular pressure


How is a carbonic anhydrase inhibitor used in mountain sickness?

Increased bicarb excretion ---therefore blood becomes more acidic --stimulates ventilation ---increases the amount of oxygen in the blood


How is a carbonic anhydrase inhibitor used in metabolic alkalosis?

--Correcting metabolic alkalosis


How is a carbonic anhydrase inhibitor used in epilepsy?

--Inhibits carbonic anhydrase in the CNS to retard abnormal and excessive discharge from CNS neurons


What are the adverse effects of a carbonic anhydrase inhibitor?

1. Metabolic Acidosis: chronic reduction in HCO3 stores
2. Hyponatremia
3. Hypokalemia: due to increased Na presented to the collecting tubule is partially reabsorbed increasing the lumen negative electrical potential and enhancing K secretion
4. Renal Stones:
5. Other effects: malaise, fatigue, depression, drowsiness, paresthesias


Moving on to Osmotic Diuretics is Mannitol, what is this used for?

Administered in large enough doses to increase the osmolality of plasma and tubular fluid
--extracting water from intracellular compartments, osmotic diuretics expand the extracellular fluid volume, decrease blood viscosity and inhibit renin release


Mannitol increase the urinary excretion of what electrolytes?

Nearly all:
--Na, K, Ca, Mg, Cl, HCO3 and phosphate


Mannitol is used for what?

Reduction of increased Intracranial pressure associated with cerebral edema
Reduction of increased intraocular pressure
Promotion of urinary excretion of toxic substances
Genitourinary irrigant


What are the adverse effects of Mannitol?

Extracellular Volume Expansion and Hyponatremia
--extracts water from cells leading to headache, nausea, and vomiting
Tissue Dehydration: as water is extracted from cells, intracellular K concentration rises


Mannitol is contraindicated in whom?

Patients with active cranial bleeding


The last set of drugs are ADH antagonists: Conivaptan. What is the action of this drug?

Inhibits the effects of ADH in the collecting tubule
--acts as an antagonist at the V1 and V2 receptors
Collecting tubule is now impermeable to water and dilute urine is produced


Conivaptan is used for what?

Euvolemic and Hypervolemic Hyponatremia


Why must conivaptan be administered IV?

Metabolized by and is a potent inhibitor of CYP3A4


What are the adverse effects of conivaptan?

1. Nephrogenic DI: severe hypernatremia and DI
2. Infusion site reactions


What are the contraindications for conivaptan?

Hypovolemic Hyponatremia
Renal Failure