Diuretics and Anti-hypertensives Flashcards
What is mannitol?
A non metabolized and non reabsorbed sugar that acts in the proximal tubule. It is considered an osmotic diuretic. It draws free water out of the tissue and into the circulation where it is excreted by the kidneys.
It is not used as an antihypertensive drug. It’s used to maintain hydration (mostly in surgical situations). It makes sure that there is maintained perfusion during transplants.
It can also be used to manage elevated intracranial pressure.
What is acetazolamide?
It is a carbonic anhydrase inhibitor that acts in the proximal tubule which results in an elimination of bicarbonate to induce metabolic acidosis.
It is used for glaucoma to decrease intraoccular pressure.
It is used to prevent acute mountain sickness (to counteract respiratory alkalosis).
Where do loop diuretics act?
They act on the Na/K/2Cl cotransporter in the thick ascending limb of the loop of henle.
What are loop diuretics used for? (4)
- Volume overload
- heart failure
- BP reduciton
- pulmonary edema
What are side effects of loop diuretics? (4)
- Decreased K/Mg
- Hypocalcemia
- Precipitate gout attack
- Metabolic alkalosis (Because loop and thiazide diuretics increase sodium delivery to the distal segment of the distal tubule, this increases potassium loss (potentially causing hypokalemia) because the increase in distal tubular sodium concentration stimulates the aldosterone-sensitive sodium pump to increase sodium reabsorption in exchange for potassium and hydrogen ion, which are lost to the urine. The increased hydrogen ion loss can lead to metabolic alkalosis.)
What is the duration of action for furosemide?
4-6 hours.
Furosemide is also called Lasix so remember la “SIX”.
Do not give before going to bed because the patient will have to wake up to urinate. It’s best to give once in the morning and another time early in the afternoon.
True or False: Torsemide has longer duration of action and greater bioavailability than furosemide
True.
Furosemide is 4-6 hours with 40-70% bioavailability.
Torsemide is 12-16 hours with 80-90% bioavailability.
Which loop diuretic would you give for a patient with sulfa allergies? Would a patient who is allergic to sulfonamide antibiotics have a reaction to loop diuretics?
Ethacrynic acid. It is the only non-sulfa containing loop or thiazide.
Patients who have allergies to sulfonamide antibiotics are not necessarily allergic to the sulfa loop diuretics. They are different.
What is the most potent loop diuretic?
Bumetanide. 1 mg of bumetanide is equal to about 20 mg of other loop diuretics.
Where do thiazide diuretics act? Do they cause much diuresis?
They act in the distal convoluted tubule at the Na/Cl cotransporter.
They don’t cause much diuresis. They are effective at achieving their antihypertensive effect without producing much urine. Typically, when a patient is started on thiazide diuretics, they will transiently have more urine production but this side effect decreases.
What are side effects of thiazide diuretics?
- Hypokalemia
- Can precipitate gout attacks
- Can cause dehydration
- Hypercalcemia (opposite of loop diuretics)
- Hyperglycemia (in patients who are at high risk of developing hyperglycemia or diabetes)
What is the most common thiazide diuretic? What might you consider if you want to have a drug with a longer half life?
Hydrochlorothiazide (very inexpensive)
Consider chlorthalidone if you want a longer halflife. It has a halflife of 40-60 hours compared to HCTZ which has 2.5. It’s more expensive though.
Which diuretic is considered “first line”?
Thiazides
What is a situation that causes thiazide diuretics to lose their efficacy?
When GFR falls below 30.
Thiazide diuretics lose efficacy in later stages of CKD as less drug reaches the site of action as the kidney fails.
More efficacious loop diuretic use is necessary when GFR is below 30 and the loop diuretics are often paired with metalozone (a thiazide that is the exception to this rule. It is very potent and can work with CKD in conjunction with loop diuretics)
What 2 thiazide diuretics are still shown to have efficacy below the 30 gfr cutoff in patients with CKD?
Chlorthalidone and metalozone
Where do potassium sparing diuretics act?
They act at the collecting tubule binding to aldosterone dependent Na/K exchangers.
Spironolactone and eplerenone competitively inhibit the mineralocorticoid receptors (with eplerenone being more specific so it has less side effects).
What are potassium sparing diuretics usually used in combination with and why?
Thiazide and loop diuretics. They are used to counter the potassium wasting (hypokalemia) effect of thiazides and loop diuretics.
What is a side effect of spironolactone?
gynecomastia (enlargement of male breasts)
True or False: ACE inhibitors and ARBs are contraindicated for pregnancy
True. Also, much of the damage is done in the first trimester before people know they are pregnant so it’s a good idea to take them off their ACE inhibitors or ARBs if they are planning on getting pregnant.
