Diuretics - Osmotic Diuretics

Question 1

What are some medications in this class?

Answer 1

Osmotic diuretics include mannitol, urea, glycerine amongst others

Question 2

What is the mechanism of action of osmotic diuretics?

Answer 2

They work by being an osmotically active molecule pulling water from the extra vascular to the intravascular space which increases the amount of fluid going into the nephrons. It also causes water retention within the permeable parts of the tubules (proximal convoluted and thin descending tubules) which will cause more water to be excreted with minimal electrolyte loss.

Question 3

What are the indications of osmotic diuretics?

Answer 3

1. They’re used to decrease intracranial pressure.
2. They’re used to treat patients with acute renal failure due to shock, drug toxicities and trauma.
3. They’re used to flush the kidneys when there’s high levels of hemoglobin (due to hemolysis) or myoglobin (due to rhabdomyolysis)

Question 4

What are the side effects of mannitol?

Answer 4

1. Renal Side effects: hypernatremia and hyperkalemia due to increased water excretion.
2. Systemic side effects:
   I. Increased plasma volume which could lead to:
   A. Worsening edematous states (e.g. pulmonary edema)
   B. Dilution of plasma (e.g. hyponatremia)
   I. Dehydration