Vasodilators Overview and Pharmacology
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Questions and Answers

Which condition is predominantly treated with hydralazine?

  • Essential hypertension (correct)
  • Hypotension
  • Myocardial infarction
  • Angina pectoris

What is the main adverse effect associated with hydralazine due to its vasodilatory effects?

  • Hyperkalemia
  • Bradycardia
  • Diabetes insipidus
  • Postural hypotension (correct)

Why is hydralazine typically combined with a beta-blocker?

  • To prevent reflex tachycardia (correct)
  • To increase cardiac output
  • To reduce sodium retention
  • To enhance renal function

What distinguishes vasodilators from other antihypertensive drugs?

<p>They act directly on the smooth muscles in arterioles and veins. (C)</p> Signup and view all the answers

Which of the following vasodilators is known for selectively dilating arterioles?

<p>Both B and C (B)</p> Signup and view all the answers

Which pharmacokinetic property distinguishes slow acetylators of hydralazine?

<p>Increased vasodilation (D)</p> Signup and view all the answers

What is the effect of arteriolar dilators on cardiac afterload?

<p>They decrease cardiac afterload. (C)</p> Signup and view all the answers

Minoxidil is reserved for which type of patient?

<p>Patients with severe hypertension unresponsive to safer drugs (A)</p> Signup and view all the answers

What is the main mechanism through which hydralazine causes vasodilation?

<p>Direct action on vascular smooth muscle (B)</p> Signup and view all the answers

What primary effect results from the dilation of capacitance vessels?

<p>Decreased cardiac work. (C)</p> Signup and view all the answers

Which vasodilator-initiated change correlates with decreased cardiac output?

<p>Decreased venous return to the heart. (D)</p> Signup and view all the answers

What adverse effect might occur in patients taking hydralazine at high doses?

<p>Systemic lupus erythematosus-like syndrome (D)</p> Signup and view all the answers

What effect does arteriolar dilation have on the heart during hydralazine treatment?

<p>Increased myocardial contractility (D)</p> Signup and view all the answers

What therapeutic implication do selectivity properties of vasodilators have?

<p>Selectivity helps in achieving desired therapeutic effects. (A)</p> Signup and view all the answers

In what clinical situation is sodium nitroprusside utilized?

<p>Emergency situations in inpatient settings. (A)</p> Signup and view all the answers

Why is postural hypotension less pronounced in recumbent subjects?

<p>Less effect of gravity on venous return (D)</p> Signup and view all the answers

Which condition requires careful dosage adjustment when treated with hydralazine?

<p>Genetic acetylation rates (D)</p> Signup and view all the answers

What immediate effect does the dilation of arterioles have on tissue perfusion?

<p>Increases tissue perfusion. (A)</p> Signup and view all the answers

What are the undesired effects related to selective dilation of vasodilators typically associated with?

<p>Alterations in blood pressure regulation. (D)</p> Signup and view all the answers

How does selective dilation affect cardiac preload?

<p>It decreases preload, affecting ventricular contraction. (D)</p> Signup and view all the answers

What is the primary cardiovascular indication for minoxidil?

<p>Severe hypertension (A)</p> Signup and view all the answers

Which adverse effect is commonly associated with the use of minoxidil?

<p>Hypertrichosis (B)</p> Signup and view all the answers

What is the mechanism through which minoxidil exerts its vasodilatory effect?

<p>Opening potassium channels in vascular smooth muscle (D)</p> Signup and view all the answers

Why should minoxidil be used with a beta-blocker and a diuretic?

<p>To minimize reflex tachycardia and fluid retention (D)</p> Signup and view all the answers

What is the half-life of minoxidil?

<p>4.2 hours (C)</p> Signup and view all the answers

What is a significant risk associated with the use of minoxidil that could lead to cardiac complications?

<p>Pericardial effusion (D)</p> Signup and view all the answers

How is minoxidil primarily eliminated from the body?

<p>Urine (D)</p> Signup and view all the answers

In which population should minoxidil use be approached with caution due to potential risks?

<p>Pregnant women (C)</p> Signup and view all the answers

What should be monitored in patients taking minoxidil to manage potential adverse effects?

<p>Daily weight and blood pressure (C)</p> Signup and view all the answers

What is a common and serious consequence of sodium and water retention caused by minoxidil?

<p>Cardiac decompensation (B)</p> Signup and view all the answers

What is the primary therapeutic effect of arteriolar dilators like hydralazine and minoxidil?

<p>Decrease cardiac afterload (B)</p> Signup and view all the answers

Which vasodilator is known to affect both arterioles and veins?

<p>Sodium nitroprusside (C)</p> Signup and view all the answers

What specifically sets vasodilators apart from other antihypertensive drugs?

<p>They act directly on vascular smooth muscle (D)</p> Signup and view all the answers

What impact do venous dilators have on cardiac preload?

<p>They decrease preload (C)</p> Signup and view all the answers

Which mechanism of action do hydralazine and minoxidil primarily share?

<p>Direct relaxation of smooth muscles (A)</p> Signup and view all the answers

What is a common adverse effect associated with the selective dilation of arterioles?

<p>Reflex tachycardia (A)</p> Signup and view all the answers

What consequence does the dilation of capacitance vessels lead to?

<p>Decrease in ventricular filling (B)</p> Signup and view all the answers

In the pharmacology of vasodilators, what effect does the selectivity of a drug have?

<p>Determines the drug's side effects (D)</p> Signup and view all the answers

Why might sodium nitroprusside be preferred in challenging clinical situations?

<p>It is a potent and rapid vasodilator (B)</p> Signup and view all the answers

How does selective dilation of arterioles influence cardiac work?

<p>It reduces cardiac work through decreased afterload (A)</p> Signup and view all the answers

Which factor is NOT a consequence of venous relaxation due to vasodilators?

<p>Increased venous return (D)</p> Signup and view all the answers

What is the primary reason for combining hydralazine with a diuretic?

<p>To prevent sodium and water retention (C)</p> Signup and view all the answers

Which statement most accurately describes the pharmacological profile of hydralazine?

<p>It selectively dilates arterioles with minimal effects on veins. (C)</p> Signup and view all the answers

Why might slow acetylators experience undesired effects from hydralazine?

<p>They accumulate higher blood levels of the drug. (D)</p> Signup and view all the answers

What adverse effect is commonly associated with the use of hydralazine in slow acetylators?

<p>Systemic lupus erythematosus-like syndrome (D)</p> Signup and view all the answers

What clinical situation is hydralazine most commonly employed?

<p>Essential hypertension treatment (B)</p> Signup and view all the answers

What cardiovascular response occurs due to the reflex mechanisms triggered by arteriolar dilation from hydralazine?

<p>Increased cardiac workload and myocardial oxygen demand (D)</p> Signup and view all the answers

What is the primary clinical goal when using minoxidil in hypertensive patients?

<p>Reduce blood pressure (B)</p> Signup and view all the answers

What is a key characteristic of minoxidil compared to hydralazine?

<p>It causes more severe adverse effects. (D)</p> Signup and view all the answers

What metabolite of minoxidil is responsible for causing potassium channels in vascular smooth muscle to open?

<p>Minoxidil sulfate (D)</p> Signup and view all the answers

In which patient demographic should minoxidil be used with caution?

<p>Patients with a history of heart failure (C)</p> Signup and view all the answers

How does the route of administration affect hydralazine's time course of action?

<p>Oral effects last shorter than parenteral effects. (D)</p> Signup and view all the answers

Which combination of medications is recommended to minimize adverse effects when using minoxidil?

<p>A beta-blocker and intensive diuretic therapy (B)</p> Signup and view all the answers

What is a significant side effect associated with minoxidil usage that affects a considerable percentage of patients?

<p>Hypertrichosis (D)</p> Signup and view all the answers

What immediate pharmacokinetic effect occurs within 2 to 3 hours after minoxidil administration?

<p>Maximum vasodilation (D)</p> Signup and view all the answers

In patients taking minoxidil, what should be monitored to prevent fluid retention-related complications?

<p>Daily weight (D)</p> Signup and view all the answers

Which of the following conditions is a known risk associated with minoxidil use?

<p>Pericardial effusion (A)</p> Signup and view all the answers

What should patients be advised to do when taking minoxidil to avoid experiencing postural hypotension?

<p>Stand up slowly (C)</p> Signup and view all the answers

Which group of patients should minoxidil be used cautiously or avoided altogether?

<p>Pregnant patients (A)</p> Signup and view all the answers

What is the elimination route for minoxidil and its metabolites from the body?

<p>Urine (B)</p> Signup and view all the answers

Flashcards

Vasodilators

Drugs used to treat high blood pressure (hypertension) and heart failure by directly relaxing the smooth muscles in blood vessels.

Selectivity of Vasodilatory Effects

The ability of a drug to target specific types of blood vessels, either arteries or veins.

Cardiac Afterload

The force the heart has to exert to pump blood.

Cardiac Preload

The amount of blood returning to the heart.

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Arteries

Blood vessels that carry blood away from the heart.

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Veins

Blood vessels that carry blood back to the heart.

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Vasodilation

The widening of blood vessels.

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Vasoconstriction

The narrowing of blood vessels.

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Blood Pressure

The force or pressure exerted by the blood against the walls of arteries.

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Cardiac Output

The amount of blood pumped by the heart in one minute.

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Postural Hypotension

A decrease in blood pressure that occurs when a person stands up quickly, often caused by a sudden drop in blood flow to the brain.

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Hydralazine's Vasodilatory Action

Hydralazine primarily dilates arterioles, causing a decrease in peripheral resistance and a drop in blood pressure.

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Hydralazine's Duration of Action (Oral)

Hydralazine's effects begin within 45 minutes after oral administration and can last up to 6 hours or longer.

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Hydralazine's Duration of Action (Parenteral)

Hydralazine's effects onset is faster with parenteral administration, taking effect within 10 minutes and lasting for 2 to 4 hours.

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Hydralazine's Metabolism and Acetylation

The ability to metabolize hydralazine is genetically determined, with some individuals being rapid acetylators and others being slow acetylators. Slow acetylators may have higher blood levels of hydralazine, increasing the risk of side effects.

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Hydralazine's Reflex Tachycardia

Hydralazine can trigger reflex tachycardia, increasing heart rate and myocardial oxygen demand. This is often managed by combining it with a beta-blocker.

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Hydralazine's Effect on Blood Volume

Hydralazine's hypotension can lead to sodium and water retention, increasing blood volume. This can be counteracted with diuretics.

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Minoxidil's Vasodilatory Action Compared to Hydralazine

Minoxidil causes more potent vasodilation than hydralazine but also has a higher risk of serious adverse reactions.

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Minoxidil's Selective Vasodilation

Like Hydralazine, Minoxidil primarily dilates arterioles, resulting in reduced peripheral resistance and lower blood pressure.

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Minoxidil's Use in Severe Hypertension

Minoxidil is a potent vasodilator used to treat severe hypertension that is unresponsive to other medications.

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How does minoxidil work?

Minoxidil is a vasodilator that works by relaxing the smooth muscle in blood vessels. It does this by causing potassium channels to open and potassium to leave the cells. This hyperpolarizes the cells, making them less likely to contract. Minoxidil is rapidly and completely absorbed after oral administration and has a half-life of about 4.2 hours.

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What is the main indication for minoxidil?

The primary use for minoxidil is to treat severe hypertension, particularly for those who have not responded well to other, safer medications. Minoxidil often is given with a beta-blocker and a diuretic to counter its side effects.

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What is a serious side effect of minoxidil?

One major side effect of minoxidil is reflex tachycardia. This means that when minoxidil lowers blood pressure, the body responds by increasing the heart rate. This can be minimized by using a beta-blocker along with minoxidil.

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What fluid imbalance can happen with minoxidil?

Another common side effect of minoxidil is fluid retention. This can lead to serious consequences, including heart failure. To manage this problem, doctors use loop diuretics, either alone or in combination with other diuretics. In severe cases dialysis may be needed.

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What common cosmetic side effect is associated with minoxidil?

Minoxidil can cause excessive hair growth (hypertrichosis). This occurs because of a change in the cells at the base of the hair follicles. This side effect usually begins on the face and later spreads to other areas of the body.

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What serious heart problems can minoxidil cause?

Minoxidil can lead to pericardial effusion, where fluid builds up around the heart, and this can progress to cardiac tamponade, a more serious condition. Minoxidil can also worsen angina pectoris by increasing cardiac oxygen demand.

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Why is minoxidil considered a last resort medication?

Because minoxidil is a powerful drug with significant side effects, it is typically reserved for patients with severe hypertension who haven't responded to other treatments. It's essential to make sure the benefits of using minoxidil outweigh the potential risks.

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What are some important considerations when using minoxidil?

When taking minoxidil, it is important to monitor blood pressure and heart rate regularly. You also need to monitor weight daily to detect fluid retention. It is also important to stand up slowly to avoid sudden drops in blood pressure.

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What is the use of hydralazine in infants and children?

Hydralazine, another vasodilator, is used in infants as young as one month old to manage chronic hypertension. Children and adolescents can also use hydralazine with careful monitoring and dose adjustments based on their age.

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What are important considerations for pregnant and breastfeeding women regarding hydralazine and minoxidil?

While hydralazine and minoxidil are options for managing high blood pressure during pregnancy, they should only be used if the benefits clearly outweigh the risks. The safety of both drugs for breastfeeding mothers is not well-established.

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Minoxidil's vasodilatory strength vs. hydralazine

Minoxidil causes more potent vasodilation than hydralazine, but carries a higher risk of adverse reactions.

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Minoxidil's effect on hair growth

Minoxidil can cause excessive hair growth, typically starting on the face and spreading to other areas.

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Minoxidil's effect on the heart (pericardial effusion)

Minoxidil can lead to fluid buildup around the heart, potentially causing a serious condition called cardiac tamponade.

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What are vasodilators?

Vasodilators are medications that relax the smooth muscles in blood vessels, leading to wider blood vessels. This widening reduces blood pressure and helps manage high blood pressure (hypertension) and heart failure.

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How do vasodilators work?

Vasodilators work by directly targeting the smooth muscles in arteries and veins, causing them to relax and expand. This action is distinct from other drugs that may indirectly affect blood vessels.

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What is selectivity in vasodilators?

Different vasodilators can target different types of blood vessels. Some mainly affect arterioles (small arteries), while others impact both arterioles and veins. This selectivity determines how they affect blood pressure and blood flow.

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How do arteriolar dilators affect cardiac afterload?

Vasodilators that primarily widen arterioles reduce the resistance the heart encounters when pumping blood. This reduces the workload for the heart and improves blood flow to tissues.

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How do venous dilators affect cardiac preload?

Vasodilators that mainly widen veins reduce the amount of blood returning to the heart. This lessens the pressure on the heart and can decrease cardiac output and blood flow to tissues.

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How do hydralazine and minoxidil affect blood pressure?

Hydralazine and minoxidil primarily target arterioles, causing dilation and reducing blood pressure by lowering resistance. This improves blood flow and reduces the heart's workload.

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How does genetics affect vasodilator response?

The effects of certain vasodilators, like hydralazine, can be influenced by a person's genetic makeup. Their ability to process the drug can vary, impacting the effectiveness and potential side effects.

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What is reflex tachycardia with vasodilators?

Some vasodilators, such as hydralazine, can trigger a reflex response where the heart beats faster to compensate for the lower blood pressure. This can increase the heart's oxygen needs.

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How can vasodilators affect blood volume?

Vasodilators can sometimes cause the body to retain water and sodium, increasing blood volume. This can counteract the effects of lowering the blood pressure, potentially requiring additional medication.

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How does minoxidil cause vasodilation?

Minoxidil's primary action is to dilate arterioles, reducing peripheral resistance and subsequently lowering blood pressure.

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What happens to minoxidil in the body?

Minoxidil is metabolized and eliminated in the urine, with a half-life of about 4.2 hours.

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Study Notes

Vasodilators: Overview

  • Vasodilators are drugs used to treat hypertension and heart failure.
  • Vasodilators act directly on smooth muscles in arterioles and veins, causing vessel relaxation—differing from other antihypertensives.
  • Examples include hydralazine, minoxidil, and sodium nitroprusside (used in emergencies).

Vasodilator Pharmacology: Basic Concepts

  • Selectivity of Effects: Vasodilators vary in the blood vessels they affect.
    • Hydralazine and minoxidil primarily dilate arterioles.
    • Nitroprusside dilates both arterioles and veins.
  • Hemodynamic Effects:
    • Arteriolar dilation decreases cardiac afterload and increases cardiac output and tissue perfusion.
    • Venous dilation reduces cardiac preload and decreases cardiac output and tissue perfusion.
  • The selectivity of a vasodilator is crucial for its therapeutic and adverse effects. Hemodynamic effects differ based on dilation of arterioles or veins, influencing cardiac work and output.

Therapeutic Uses

  • Vasodilators are used for essential hypertension, hypertensive crisis, angina, heart failure, and myocardial infarction.
  • Specific uses depend on the drug's pharmacological profile (route, site of action, intensity, and duration of effects).

Adverse Effects

  • Postural Hypotension: Venous dilation causes blood pooling, reducing venous return to the heart, and decreasing blood pressure. This effect is less pronounced in recumbent patients.
  • Vasodilators increase the risk of falls due to hypotension. Patients should be instructed to avoid abrupt transitions to an upright position. Slow transitions minimize hypotension.

Hydralazine

  • Cardiovascular Effects: Selective arteriolar dilation, minimal effect on veins. Lowers peripheral resistance and blood pressure. Increases heart rate and myocardial contractility (reflex).
  • Pharmacokinetics: Readily absorbed orally. Effects begin within 45 minutes (oral) and 10 minutes (parenteral), lasting 6+ hours or 2-4 hours respectively. Metabolized via acetylation; slow acetylators have higher blood levels and more significant adverse effects. Dosage should be adjusted for slow acetylators to avoid accumulation.
  • Therapeutic uses: Essential hypertension (often with a beta-blocker), commonly replaced by newer agents. Short-term use in heart failure (reducing afterload), often with isosorbide dinitrate.
  • Adverse Effects:
    • Reflex tachycardia: often severe; combined with beta-blocker.
    • Increased blood volume: sodium and water retention. Use with diuretics.
    • SLE-like syndrome (rare, most common in slow acetylators): discontinue hydralazine if this occurs. Symptoms are reversible but may take several months to resolve, often with a dosage limit of <200mg/day.

Minoxidil

  • Cardiovascular Effects: More potent arteriolar dilation than hydralazine, resulting in greater blood pressure reduction. Direct action on vascular smooth muscle, requiring metabolism to minoxidil sulfate for effect.
  • Pharmacokinetics: Rapidly absorbed orally, peak effect in 2-3 hours, residual effects for 2 days. Extensive metabolism.
  • Therapeutic Uses: Reserved for severe, uncontrolled hypertension. Use with beta-blockers and intensive diuretics to minimize adverse effects.
  • Adverse Effects:
    • Reflex tachycardia.
    • Sodium and water retention (potentially severe, requiring diuretics or dialysis).
    • Hypertrichosis (excessive hair growth) in 80% of patients. Black Box Warning: pericardial effusion and exacerbation of angina. Hypertrichosis is a common and often bothersome side effect.
  • Minoxidil Black Box Warning: This drug has a specific black box warning about potential pericardial effusion (accumulation of fluid around the heart) which can lead to tamponade (pressure on the heart), and exacerbating angina (chest pain).

Summary Prescribing Considerations

  • Goal: Lower blood pressure (hypertension) or reduce afterload (short-term heart failure). Use in reduced doses to manage hypotension when combined with other antihypertensives.
  • Baseline Data: Weight, vital signs.
  • Monitoring: Daily blood pressure, heart rate (patients). Daily weight (minoxidil).
  • High-Risk Patients: Avoid in pregnancy if possible.
  • Therapeutic Effects: Monitor for decreased blood pressure & improvement in heart failure symptoms.
  • Minimizing Adverse Effects: Start at low doses. Advise slow transitions from positions to avoid postural hypotension. Educate patients on symptoms of hypotension (lightheadedness, dizziness) and strategies (sitting/laying down) for symptom relief.

Patient-Centered Care Across the Life Span

  • Infants: Hydralazine used for chronic hypertension as young as 1 month old.
  • Children/Adolescents: Hydralazine can be used safely in smaller doses, similar adverse effects to adults.
  • Pregnant Women: Benefits of hydralazine/minoxidil should outweigh risks.
  • Breastfeeding Women: Limited information on drug transmission.
  • Older Adults: Monitor for falls due to increased risk of polypharmacy and orthostatic hypotension. Educate patients about slow transitions between positions and potential for hypotension.

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Description

This quiz covers the key concepts of vasodilators, including their pharmacological effects and therapeutic uses. Understand how different vasodilators like hydralazine and nitroprusside work on blood vessels to treat hypertension and heart failure. Test your knowledge on the selectivity and hemodynamic effects crucial for effective treatment.

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