Sketchy Pharm: Thiazides

Question 1

Just like the PCT and loop of Henle, the basolateral side of the DCT absorbs sodium with a ____________.

Answer 1

Na/K exchanger (like the mom giving her kid a banana and taking his peanuts in the background)

Question 2

_____________ is actively absorbed in the DCT but does not create a gradient.

Answer 2

NaCl (like the maintenance worker scraping NaCl crystals off the slide)

Question 3

True or false: calcium is dragged into the DCT epithelium by the gradient created by the NaCl pump.

Answer 3

False. Calcium is actively absorbed by a pump that is regulated by PTH.

Question 4

Thiazides inhibit ____________.

Answer 4

the NaCl transporter (like the kid with pasty thighs distracting the maintenance workers and causing them to spill NaCl into the pool)

Question 5

Thiazides are often used for ______________.

Answer 5

mild to moderate hypertension (like the pipes that are swollen but not bursting behind the DCT slide)

Question 6

Thiazides cause the increased absorption of ___________.

Answer 6

calcium (like the kid spilling his calcium from the slide onto the worker)

This can also be used to treat recurrent calcium kidney stones (like the worker scooping rocks out of the way of the calcium kid).

Question 7

True or false: thiazides improve the mortality of those with CHF.

Answer 7

False. They can help treat the symptoms of CHF but have not been shown to decrease mortality.

(There is a floppy heart balloon, but there’s no angel!)

Question 8

Why is hydrochlorothiazide often used for DI?

Answer 8

Thiazides cause a transient hypovolemia that induces more Na absorption in the proximal parts of the nephron.

(Think of the DI fountain peeing into the pool.)

Question 9

Because hydrochlorothiazides increase absorption of calcium, they are often used in those with ________________.

Answer 9

osteoporosis

Question 10

In addition to hypercalcemia, thiazides can also cause high levels of what serum markers?

Answer 10

• Glucose and LDL (butter and candy on tray trying to lure thigh kid away from high dive)
• Uric acid (girl knitting in line)
• Lithium (“LIfTium” balloons)

Question 11

Similar to furosemide, thiazide can decrease levels of ______________.

Answer 11

potassium (kid throwing banana peel from high dive ladder)

Question 12

Hydrochlorothiazides can cause hyponatremia, but furosemides can’t. Why?

Answer 12

Furosemide blocks the ascending loop of Henle channels that are responsible for creating the medullary concentration gradient. As such, urine is not able to be concentrated and sodium is lost WITH water –preserving the water/sodium balance in the blood.

Thiazide diuretics, on the other hand, do not destroy the medullary concentration gradient. Because of this, urine can still be concentrated by the selective resorption of water in the collecting duct. The excess water leads to hyponatremia.

Question 13

What side effects can be seen with thiazide use?

Answer 13

• Hyponatremia (described in another card)
• Hyperglycemia, -lipidemia, uricemia, and calcemia (also described in another card)
• Contraction alkalosis (guy squeezing OH- bottle)
• Sulfa reaction (kids throwing eggs)
• Hypokalemia (described elsewhere)

Question 14

What are the two main ways by which contraction alkalosis develops?

Answer 14

• Increased aldosterone (from low volume states) causes increased Na absorption and H+ excretion
• Increased angiotensin II (also from low volume activation of the RAAS pathway) leads to increased bicarb absorption in the PCT