Osmotic diuretics and ADH antagonists

Question 1

What are the contraindications for osmotic diuretics

Answer 1

Absolutely contra’d in

Anuric patients - they are used in acute renal failure as long as some kidney function remain, and also after crush syn or myoglobinuria, but if anuria has set in the are completely contraindicated

Head trauma patients - they are also used to lower ICP, but can actually worsen it if the elevation is due to trauma

Acute pulmonary edema- PE is one of the potential side effects of mannitol as it pulls water out of the cells into the extracellular compartment

Question 2

What are the side effects of osmotic diuretics

Answer 2

Dehydration from extremely potent diuresis

Exacerbation of heart failure from increased EC space

Pulmonary edema from increased EC space

Acute hypovolemia, hypotension, syncope

Question 3

What are the indications for mannitol

Answer 3

Increased intracranial pressure NOT due to trauma

Acute severe glaucoma

Myoglobinemia and crush syndrome.

Question 4

What are the ADH inhibitors?

Answer 4

Tolvaptan and Conivaptan

Tolvaptan is selective for the V2 Vasopressin/ADH receptor located in kidneys. - Used to treat SIADH secretion, causing urine dilution.

Conivaptan is non-selective -inhibits ADH receptors in the kidney and vassopressin 1 receptors in the vessels, causing vasodilation and urine dilution.

Used to treat SIADH and refractory edemas.

Question 5

What are the ADH receptor agonists?

Answer 5

Desmopressin - selective V2 receptor agonist.
Just concentrates urine, used to treat CNS Diabetes Insipidus

Ornipressin - Selective V1 agonist.
Acts as a vasopressor, used like epinephrine as adjunct for local anesthetics.