Sketchy Pharm: Acetazolamide, Mannitol Flashcards
In the proximal convoluted tubule, roughly 65% of _____________ are absorbed and roughly 100% of ______________ are absorbed.
electrolytes; glucose and amino acids
Sodium enters the serum on the basolateral side of the PCT via what membrane channel?
The Na/K exchanger (like the mom taking the sodium out of the gray track –from the kid –and giving him a banana)
This creates a gradient that pulls sodium across from the apical side near the lumen all the way to the blood.
Through what channel does sodium enter the PCT epithelium?
The Na/H exchanger (like the guy giving kids peanuts – Na –as they walk into the gray lane and forcing them to put on H+ Helme+s as they walk into the yellow lane)
How does carbonic anhydrase aid water reabsorption?
It converts H+ and bicarb to water and CO2 in the lumen (like the CAR Battery Anhydrase getting put in the biCARb with the H+-wearing kid in the yellow lane) and then water and CO2 passively diffuse into the PCT cells (like the water and exhaust trailing behind the kid who’s turned into the PCT gray lane).
Note: because water and solutes are dragged across the membrane, the osmolarity difference across the apical membrane is actually small.
After carbonic anhydrase breaks water and CO2 back into bicarb and H+, the ____________ gets recycled back into the lumen.
H+
Meanwhile, the bicarb is resorbed into the interstitium.
How does acetazolamide lead to natriuresis?
The net effect of carbonic anhydrase is to absorb bicarb and Na+. Inhibiting this leads to excretion of bicarb and Na+.
(Think of the gocart with the broken anhydrase battery –the biCARb is stuck in the track, and the worker who’s come to help is spilling his peanuts [Na] in the lumen. Those peanuts and bicarb should have been absorbed, which would have created a gradient to pull water in.)
Acetazolamide produces what kind of pH disturbance?
Type 2 non-anion gap metabolic acidosis (from pure loss of bicarb)
(Think of the “Close the Gap #2” sign on the edge of the track.)
Why is acetazolamide used to treat glaucoma?
The ciliary body produces aqueous humor by secreting bicarb into the lumen of the eye. It uses carbonic anhydrase to do so. Without it, less aqueous humor is produced.
(Think of the mom spilling the two eye-shaped cups.)
In addition to glaucoma, acetazolamide is also used to treat _______________.
- pseudotumor cerebri – idiopathic intracranial hypertension (like the balloon in the shape of a head with the forehead swollen)
- high-altitude sickness (like the guy scared of the tall podium)
Increasing the alkalinity of the urine (such as with bicarb) is useful in what two disorders?
- Cystine kidney stones
- Uric acid kidney stones
(Both of these substances are more soluble in alkaline solutions.)
What are the side effects of acetazolamide?
- Hypokalemia (because the unabsorbed sodium goes to the collecting duct and is exchanged for excreted potassium)
- Type 2 renal tubular acidosis
- Calcium phosphate stone formation
- Sulfur allergy
(Think of the banana peel on the track, the Mario-looking racer with two tubes of acid, the brown phosphate stones, and the rotten eggs.)
How does mannitol work?
It is an osmotic diuretic that pulls water into the PCT and descending loop of Henle (like the MAN who is TaLl pouring water on the kid on fire).
Like acetazolamide, mannitol is also used for _________________.
glaucoma (eye cups) and cerebral edema (red head balloon next to tall guy)
What adverse effects can mannitol cause?
Pulmonary edema from temporary expanse in intravascular fluid (like the kid with the lung stains on his shirt)
Note: this is why it should not be given to those with CHF.
Mannitol can cause both hypernatremia and hyponatremia. What???? Explain how this happens.
The temporary expanded volume from initial mannitol use can lower the sodium concentration. Prolonged use will lead to selected water loss which will produce hypernatremia.
