Nephron Function and Diuretics

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Questions and Answers

Why is diuresis scanty in the distal tubule?

There is a high concentration of potassium in the distal tubule.

Most Na has already been reabsorbed before reaching the distal tubule. (correct)

The distal tubule is impermeable to Na.

The distal tubule is responsible for the majority of Na reabsorption.

What is the mechanism of action of Triamterene/Dyrenium?

It enhances aldosterone activity in the distal nephron.

It disrupts Na-K exchange in the distal nephron by direct inhibition. (correct)

It promotes K secretion and reduces Na reabsorption.

It increases Na-K exchange in the distal nephron.

What is the effect of Triamterene/Dyrenium on Na excretion?

It increases Na excretion. (correct)

It has no effect on Na excretion.

It leads to Na retention.

It decreases Na excretion.

What is the effect of Triamterene/Dyrenium on K secretion?

It reduces K secretion. Signup and view all the answers

What is the primary effect of Triamterene/Dyrenium on K levels?

It conserves K. Signup and view all the answers

What is Triamterene/Dyrenium classified as?

Non-aldosterone antagonist. Signup and view all the answers

What is the extent of diuresis caused by Triamterene/Dyrenium?

Minimal diuresis. Signup and view all the answers

Where does Triamterene/Dyrenium act to disrupt Na-K exchange?

Distal tubule. Signup and view all the answers

What is the primary benefit of using nifedipine over verapamil in patients with certain disorders?

It is less likely to exacerbate AV block, heart failure, bradycardia, or sick sinus syndrome Signup and view all the answers

What is the primary mechanism of action of hydralazine?

Dilation of arterioles, reducing peripheral resistance Signup and view all the answers

What is a contraindication for the use of hydralazine?

Coronary artery disease Signup and view all the answers

What is the effect of aldosterone on the distal nephron?

It stimulates the synthesis of pumps responsible for sodium and potassium transport. Signup and view all the answers

Where does furosemide act in the nephron?

In the thick segment of the ascending limb of the loop of Henle Signup and view all the answers

What is the benefit of combining hydralazine with a beta blocker?

Preventing reflex tachycardia Signup and view all the answers

What is a potential risk of using hydralazine in older adults?

High risk for falls due to polypharmacy and orthostatic hypotension Signup and view all the answers

What is the effect of furosemide on renal blood flow and GFR?

It has no effect on renal blood flow and GFR Signup and view all the answers

What is the benefit of using nifedipine in patients with heart failure?

Reducing the risk of overt heart failure Signup and view all the answers

What is the MOA of hydrochlorothiazide?

It promotes urine production by blocking reabsorption of Na and Cl in the early segment of the distal convoluted tubule Signup and view all the answers

What is the effect of spironolactone on sodium excretion?

It decreases sodium excretion Signup and view all the answers

What is the recommended patient education for those taking nifedipine or hydralazine?

Recording anginal episodes, blood pressure, and adverse effects Signup and view all the answers

What is the current status of hydralazine in antihypertensive therapy?

It has been replaced by newer antihypertensive medications Signup and view all the answers

What is the effect of spironolactone on potassium levels?

It increases potassium levels Signup and view all the answers

Where does spironolactone act in the nephron?

In the distal nephron Signup and view all the answers

What is the MOA of spironolactone?

It blocks the action of aldosterone in the distal nephron Signup and view all the answers

What is the effect of furosemide on water reabsorption?

It decreases water reabsorption Signup and view all the answers

What is the effect of hydrochlorothiazide on urine production?

It increases urine production Signup and view all the answers

What is a necessary consideration before starting a specific medication?

Cardiac function and kidney function Signup and view all the answers

What is the primary purpose of the medication discussed?

To manage chronic angina Signup and view all the answers

What is a potential effect of the medication on the heart?

Increased QT wave duration Signup and view all the answers

What is not a purpose of the medication discussed?

To treat acute angina Signup and view all the answers

What should be evaluated before starting the medication?

Renal function and cardiac function Signup and view all the answers

What is a condition that the medication does not treat?

Acute angina Signup and view all the answers

What is a relevant aspect of the medication's effects?

Its impact on the QT wave Signup and view all the answers

What is a separate condition mentioned in the context?

Vitamin B12 deficiency Signup and view all the answers

What is the primary effect of Triamterene/Dyrenium on the distal tubule?

Inhibition of Na reabsorption Signup and view all the answers

What is the consequence of Triamterene/Dyrenium's action on Na-K exchange?

Increased Na excretion and decreased K excretion Signup and view all the answers

What is the mechanism of Triamterene/Dyrenium's action on the kidney?

Inhibition of the Na-K pump Signup and view all the answers

What is the effect of Triamterene/Dyrenium on blood pressure?

Decrease in blood pressure Signup and view all the answers

What is the classification of Triamterene/Dyrenium?

Potassium-sparing diuretic Signup and view all the answers

What is the effect of Triamterene/Dyrenium on the heart?

Decrease in cardiac workload Signup and view all the answers

What is the primary site of action of Triamterene/Dyrenium?

Distal tubule Signup and view all the answers

What is the consequence of Triamterene/Dyrenium's inhibition of Na-K exchange?

Decreased Na reabsorption and decreased K secretion Signup and view all the answers

What is the effect of Triamterene/Dyrenium on potassium levels?

Increase in potassium levels Signup and view all the answers

What is the therapeutic use of Triamterene/Dyrenium?

Treatment of hypertension Signup and view all the answers

Study Notes

Aldosterone and Diuretics

Aldosterone promotes sodium-potassium exchange by stimulating cells of the distal nephron to synthesize more pumps responsible for sodium and potassium transport.
Furosemide (Loop diuretic) MOA:
- Acts in the thick segment of the ascending limb of the loop of Henle
- Blocks reabsorption of Na and Cl
- Prevents reabsorption of water, leading to profound diuresis even when renal blood flow and GFR are low
Hydrochlorothiazide (Thiazide diuretic) MOA:
- Steroid derivative
- Promotes urine production by blocking reabsorption of Na and Cl in the early segment of the distal convoluted tubule
- Increases flow of urine
Spironolactone (Aldosterone Antagonist, potassium-sparing diuretic) MOA:
- Blocks the action of aldosterone in the distal nephron
- Leads to retention of K and excretion of Na
- Diuresis is scanty because most Na has already been reabsorbed before reaching the distal tubule
Triamterene (Non-aldosterone antagonist, potassium-sparing diuretic) MOA:
- Disrupts Na-K exchange in the distal nephron by direct inhibition
- Decreases Na reabsorption and reduces K secretion, leading to increased Na excretion and K conservation
- Minimal diuresis

Hydralazine

MOA: Dilates arterioles, decreasing peripheral resistance and lowering arterial BP
Use: HTN crisis, HF (reduces afterload for a short time in CHF)
Can be used in infants 1 month
Was common in the past, now replaced by newer anti-HTN meds
Requires combination with BB to prevent reflex tachycardia
CI: CAD, angina attacks
High risk for falls in older adults (polypharmacy and orthostatic hypotension)

Nifedipine

Use: Long-term use reduces rates of overt heart failure, coronary angiography, and coronary bypass surgery
No effect on rates of stroke, myocardial infarction, or death
Preferred over verapamil for patients with AV block, heart failure, bradycardia, or sick sinus syndrome
Pt education: Record anginal episodes, BP, AE

Pathophysiology of HF

Review patho and stages of HF (4 stages)

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Description

This quiz covers the function of the nephron, including the role of aldosterone in sodium and potassium transport, and the mechanism of action of furosemide, a loop diuretic.