Diuretics Flashcards
In fluid homeostasis, dilute urine is produced if what happens?
Water intake is excess
In fluid homeostasis, concentrated urine is produced if what happens?
Large amounts of water are loss
What are the two key players in fluid homeostasis?
Hormones
- Aldosterone
- Antidiuretic Hormone (ADH)
Fill in the blank:
ADH functions primarily by its influence on ________ ____ and ______ ___________ via urine excretion.
fluid loss; fluid retention
What functions primarily by its influence on the sodium content of the extracellular fluid?
Aldosterone
Besides sodium, what is another trigger for aldosterone?
Renin-Angiotensin-Aldosterone Axis
What are the three effects of Angiontensin II?
What is the net result of these three effects?
Effects
- Increased thirst
- Increased ADH from posterior pituitary
- Increased aldosterone from adrenal gland
Net Result
- Increased fluid volume
- Increased BP
What three things must decrease in order for ADH to be released from the posterior pituitary?
- Blood volume drops
- Arterial blood pressure drops
- Amount of filtrate (GFR) drops
What picks up the signal from kidneys of GFR decrease?
Where are they located?
Osmoreceptors
Hypothalamus
What releases ADH?
Posterior pituitary
ADH causes the renal tubules to increase what?
This causes what two things to occur?
Water reabsorption
- Blood volume comes back up
- Blood pressure comes back up
ADH impacts blood pressure in two ways.
- In smaller amounts, it does what?
- In large amounts it acts as what? Which causes?
- In smaller amounts, it inhibits urine production.
- In large amounts, it acts as a vasoconstrictor ⇢ BP goes up
When aldosterone levels are sufficient, an adequate number of Na+ ions are what?
Reabsorbed
For each Na+ ion reabsorbed, what two things happen?
- 1 Cl- ion follows it (reabsorbed)
- 1 K+ ion secreted into filtrate and excreted via urine
As aldosterone levels increase, what happens to
- serum Na+ levels?
- serum K+ levels?
- serum Na+ increases
- serum K+ decreases
This restores balance for both Na+ and K+
What happens when there are rising K+ or falling Na+ levels in ECF?
Adrenal gland releases aldosterone
What happens to water when Na+ is reabsorbed into filtrate?
Water follows it passively into blood
Renin-Angiotensin-Aldosterone Axis is a system of chemical reactions that help to regulate what two things?
- Blood pressure
- Fluid balance
What enzyme does the juxtaglomerular apparatus secrete in response to a decrease blood flow to kidneys?
This sets a series of rections called what?
Renin
Renin-Angiotensin-Aldosterone Axis
What is creatinine clearance?
How much creatinine / drugs you clear from kidneys over a measurement of time.
What is glomerular filtration rate (GFR)?
How much urine your kidneys make over a measurement of time.
What are diuretics?
Drugs that accelerate the rate of urine production
Diuretics are responsible for the removal of what?
Sodium and water
What are the five classes of diuretics?
- Carbonic anhydrase inhibitors (CAIs)
- Loop diuretics
- Osmotic diuretics
- Potassium-sparing diuretics
- Thiazide and thiazide-like diuretics
Finish this sentence:
Where Na+ goes ⇢ _____________
water follows
What percentage of sodium is reabsorbed at the loop of Henle?
20 to 25%
What percentage of sodium is reabsorbed in the distal tubules?
5 to 10%
What percentage of sodium is reabsorbed in the collecting ducts?
3%
What happens to the sodium not reabsorbed?
Excreted in urine
What are the two CAIs?
- Acetazolamide (Diamox)
- Methazolamide (Neptazane)
Which CAI is not indicated for a diuretic?
Methazolamide (Neptazane)
What are both CAIs indicated for?
- Glaucoma
- High altitude sickness
What is the route of Acetazolamide (Diamox)?
PO / IV
(CAI)
What is the route for Methazolamide (Neptazane)?
PO
(CAI)
What is the MOA for CAIs?
- Block action of anhydrase enzyme
- Reduces [] of H+ in proximal tubules
- Prevents exchange of H+ and Na+ and water
- Increases excretion of
- HCO3-
- Na+
- H2O
- K+
- Resorption of water is decreased and urine output is increased
What does the enzyme carbonic anhydrase do?
Makes H+ ions available for exhange with Na+ and water proximal tubule
True or False:
CAIs are more potent than loops or thiazides.
False
(They are less potent)
How are CAIs used in the long-term management of open-angle glaucoma?
Adjunct agents
CAIs are sometimes used with miotics to do what?
Lower IOP (intraocular pressure) prior to ocular surgery
What are four other indications for CAIs other than glaucoma?
- High altitude sickness
- HF
- Edema
- Epilepsy (rarely)
Acute mountain sickness happens because, as barometric pressure decreases, % of O2 stays the same.
- What happens to the number of O2 molecules per breath?
- What happens because of this?
- Decreases
- Hypobaric hypoxia
What are eight adverse / side effects of CAIs?
- Photosensitivity
- Urticaria
- Metabolic acidosis
- Anorexia
- Hematuria
- Drowsiness
- Paresthesias
- Melena
What are the four loop diuretics?
- Furosemide (Lasix)
- Bumetanide (Bumex)
- Torsemide (Demadex)
- Ethacrynic acid (Edecrin)