Updated: 2/24/2018

Proximal Tubule Diuretics

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Questions
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Evidence
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Overview
 

 
Snapshot
  • A 32-year-old previously healthy man develops headache, fatigue, vomiting, and shortness of breath about 12 hours after arriving to Mt. Everest Base Camp. Over the next day, he develops mild difficulty walking, and confusion. He is seen by a physician who administers a medication and advises him to rest. His symptoms improve over the next 24-48 hours. (Acetazolamide)
Mannitol
  • Mechanism 
    • osmotic diuretic
      • increases osmotic pressure of the glomerular filtrate
        • this in turn impairs tubular reabsorption of water and electrolytes
  • Clinical use
    • oliguria
      • which can result from shock and trauma
    • drug overdose
      • promotes urinary excretion of toxic substances
    • glaucoma
      • ↓ intraocular pressure
    • increased intracranial pressure
      • especially in the setting of cerebral edema
  • Toxicity 
    • pulmonary edema 
    • congestive heart failure (CHF) exacerbation
    • hypovolemia
  • Contraindications
    • anuria
    • CHF
Acetazolamide
  • Mechanism
    • carbonic anhydrase inhibitor
      • blocks reabsorption of bicarbonate
        • dissociation of carbonic acid into water and carbon dioxide in the proximal tubule prevented
      • bicarbonate in the lumen then binds to sodium to form sodium bicarbonate which is excreted
    • results in sodium bicarbonate diuresis and ↓ total body bicarbonate
      • loss of bicarbonate results in metabolic acidosis
  • Clinical use
    • glaucoma
    • urinary alkalinization
    • metabolic alkalosis
    • altitude sickness
    • increased intracranial pressure
      • especially for idiopathic intracranial hypertension
  • Toxicity
    • hyperchloremic metabolic acidosis (non-anion gap)
    • type 2 renal tubular acidosis
    • hypokalemia
    • neuropathy/parasthesias
    • ↑ renal stone production
      • calcium phosphate stones
    • ammonia toxicity
    • sulfa allergy
 

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Questions (2)

(M1.RL.13.6) A 56-year-old male with history of CHF presents to a trauma center following a motor vehicle accident. On arrival, his Glasgow Coma Scale score is 8, and he is found to have increased intracranial pressure. Mannitol is administered. Which of the following side effects of the drug would you most likely observe in this patient? Tested Concept

QID: 100960
1

Blood dyscrasias

7%

(36/482)

2

Seizures

20%

(96/482)

3

Pulmonary edema

49%

(236/482)

4

Arrhythmias

20%

(96/482)

5

Restrictive cardiomyopathy

3%

(13/482)

M 3 E

Select Answer to see Preferred Response

(M1.RL.13.48) A 61-year-old male is given acetazolamide to treat open-angle glaucoma. Upon diuresis, his urine is found to be highly alkaline. Which of the following accounts for the alkaline nature of this patient’s urine? Tested Concept

QID: 101002
1

Inhibition of chlorine reabsorption in the thick ascending loop of Henle

5%

(9/179)

2

Inhibition of chlorine reabsorption in the distal convoluted tubule

10%

(18/179)

3

Inhibition of acid secretion in alpha-intercalated cells

7%

(12/179)

4

Inhibition of bicarbonate reabsorption in the proximal tubule

61%

(110/179)

5

Inhibition of bicarbonate reabsorption in beta-intercalated cells

9%

(17/179)

M 1 E

Select Answer to see Preferred Response

Evidence (2)
Topic COMMENTS (22)
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