Drugs for Tachycardia
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Questions and Answers

What is the mechanism of action for direct thrombin inhibitors like Dabigatran?

  • Inhibit thrombin (correct)
  • Inhibit Factor X directly
  • Activate antithrombin III
  • Inhibit platelet activation via P2Y12 receptors

Which of the following anticoagulants is a direct inhibitor of Factor X?

  • Warfarin
  • Xaban (correct)
  • Heparin
  • Dabigatran

What is a significant adverse drug reaction associated with Clopidogrel?

  • Increased blood pressure
  • Renal impairment
  • Synergistic bleeding (correct)
  • Pulmonary embolism

Which condition is a therapeutic use for administering direct thrombin inhibitors?

<p>Atrial fibrillation (C)</p> Signup and view all the answers

Which of the following P2Y12 antagonists is a prodrug and ineffective in poor metabolizers?

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

Which drug acts as a selective Beta-1 adrenoreceptor agonist and is used for heart failure?

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

What is a contraindication of Warfarin?

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

Which drug method of action involves inhibiting the enzyme phosphodiesterase to elevate cAMP levels?

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

Calcium Channel Blockers are effective for which type of angina?

<p>Variant angina (C)</p> Signup and view all the answers

What is a common adverse effect associated with sympathomimetic amines used in heart failure?

<p>Lactic acid buildup (C)</p> Signup and view all the answers

Which type of drug inhibits the production of active vitamin K and is described as a 'Vitamin K antagonist'?

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

What distinguishes Nicorandil from other nitrate alternatives?

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

Which calcium channel blocker is noted for having a long duration of action and is often used when beta-blockers are ineffective?

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

What is the mechanism of action of Alteplase?

<p>Activates plasminogen to degrade fibrin (A)</p> Signup and view all the answers

For which condition is Tranexamic acid primarily used?

<p>Heavy menstrual cycle (C)</p> Signup and view all the answers

Which of the following is a contraindication for Statins?

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

What is the adverse effect associated with the use of Statins?

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

What therapeutic use is indicated for Eptifibatide?

<p>Cardiac surgery (A)</p> Signup and view all the answers

What mechanism does Ezetimibe utilize to lower cholesterol levels?

<p>Cholesterol transport inhibition (A)</p> Signup and view all the answers

Which of the following is a common adverse effect of Fibrinolytics?

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

What is a key property of Aspirin's action on platelets?

<p>Irreversible inhibition of COX-1 (A)</p> Signup and view all the answers

What is a therapeutic use of Streptokinase?

<p>Post myocardial infarction treatment (C)</p> Signup and view all the answers

Which of the following agents is known to stimulate vWF release?

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

What is the primary mechanism of action of Diltiazem?

<p>Blocks Ca2+ (L-type) (C)</p> Signup and view all the answers

Which type of cardiac drug is Digoxin classified as?

<p>Na+/K+ pump inhibitor (C)</p> Signup and view all the answers

In what condition is Adenosine primarily indicated for use?

<p>Acute supraventricular tachycardia (D)</p> Signup and view all the answers

What is a contraindication for the use of Digoxin?

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

What is a common adverse effect of Adenosine administration?

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

What effect does Diltiazem have on the myocyte action potential?

<p>Decreases the amplitude of AP (A)</p> Signup and view all the answers

What is the action of IV Atropine in cardiac conditions?

<p>Non-specific muscarinic antagonist (C)</p> Signup and view all the answers

Which drug is known for causing a risk of developing tolerance with prolonged use?

<p>Glyceryl Trinitrate (A)</p> Signup and view all the answers

What therapeutic use is associated with IV Dobutamine?

<p>Increase heart rate (B)</p> Signup and view all the answers

Which of the following represents an effects of negative inotropy caused by Diltiazem?

<p>Decreased force of contraction (C)</p> Signup and view all the answers

What is the main mechanism of action for Class 1b drugs?

<p>Block Na+ channels (A)</p> Signup and view all the answers

Which of the following is a contraindication for the use of Amiodarone?

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

Which drug is an example of a Class 1c antiarrhythmic?

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

What therapeutic effect does Verapamil provide?

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

Class lll drugs are primarily known to block which type of channels?

<p>K+ channels (C)</p> Signup and view all the answers

Which of the following adverse effects is commonly associated with Sotalol?

<p>Fatigue and dizziness (A)</p> Signup and view all the answers

What effect does Amiodarone have on heart rate relative to its mechanism of action?

<p>It decreases heart rate (C)</p> Signup and view all the answers

What defines the therapeutic use of Class 1a drugs?

<p>Control ventricular rate during atrial fibrillation (D)</p> Signup and view all the answers

Which of the following statements about Class 1 drugs is incorrect?

<p>All Class 1 drugs block K+ channels (B)</p> Signup and view all the answers

What adverse effect may arise from the use of Class 1c antiarrhythmic drugs?

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

Flashcards

Isosorbide mononitrate

A daily-taken oral nitrate used to treat angina.

Nicorandil

A nitrate alternative that doesn't cause tolerance and may directly activate guanylate cyclase, leading to hyperpolarization.

Calcium Channel Blockers (CCB)

Drugs that decrease oxygen demand by inhibiting myocardial contractility and reducing afterload, helpful for variant angina.

Dihydropyridines (CCB)

A type of calcium channel blocker with long duration of action, used when beta-blockers may not work; includes amlodipine and nifedipine.

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Amlodipine

A dihydropyridine CCB that inhibits L-form calcium channels in all states.

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Warfarin (Anticoagulant)

Inhibits the production of active vitamin K, and is a ‘Vitamin K antagonist’.

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Sympathomimetic Amines

Increase heart rate by acting on beta-1 adrenoreceptors.

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Dobutamine (Inotropic Agent)

Selective beta-1 adrenoreceptor agonist, increases cAMP, and enhances Ca entry, used for heart failure and shock.

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Aspirin's mechanism

Aspirin inhibits cyclooxygenase (COX-1) in platelets, decreasing cAMP and cGMP, acting as a vasodilator.

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Aspirin's effect on cAMP & cGMP

Aspirin decreases both cAMP and cGMP levels, a key step in its anti-clotting effect.

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Abciximab mechanism

Abciximab is a monoclonal antibody that prevents fibrinogen from binding to GPIIb/IIIa receptors, stopping platelet aggregation.

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Fibrinolytics' action

Fibrinolytics promote the breakdown of fibrin strands in blood clots.

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Alteplase's use

Alteplase (a recombinant tPA) is mainly used to treat strokes and acute thrombotic/embolic events, such as post-MI.

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Tranexamic acid's action

Tranexamic acid is a procoagulant that blocks fibrin degradation. It helps create clots.

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Mechanism of Statins

Statins inhibit HMG-CoA reductase, lowering cholesterol synthesis.

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Ezetimibe's effect

Ezetimibe inhibits cholesterol absorption, reducing cholesterol levels.

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Vitamin K's role

Vitamin K is crucial for the production of clotting factors.

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Desmopressin's function

Desmopressin stimulates the release of von Willebrand factor (vWF), important for blood clotting.

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Diltiazem's effect on nodal AP

Diltiazem decreases the amplitude of the nodal action potential (AP) and increases its duration (effective refractory period, ERP).

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Diltiazem's effect on myocyte AP

Diltiazem has a negative inotropic effect on myocytes, decreasing the duration of their AP. This can be risky in ventricular tachycardias.

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Digoxin mechanism of action

Digoxin inhibits the Na+/K+ pump, which pumps out 3 Na ions for every 3 K ions pumped in after an action potential (AP). This indirectly increases Ca levels in the heart, leading to increased heart rate.

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Digoxin's therapeutic effects

Digoxin increases heart rate by increasing intracellular Ca in myocytes. This is used for heart failure treatment and relieving ventricular tachycardia.

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Adenosine's mechanism of action

Adenosine activates A1 receptors and Gi receptors in the AV node, increasing K+ permeability and hyperpolarizing the node. This slows down heart rate.

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IV Atropine in bradycardia

Atropine is a non-specific muscarinic antagonist used for short-term treatment of bradycardia. It blocks the effects of acetylcholine, which slows down heart rate.

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IV Adrenaline in bradycardia

Adrenaline is a non-specific adrenergic agonist used for short-term treatment of bradycardia. It stimulates beta 1 receptors in the heart, increasing heart rate.

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IV Dopamine in bradycardia

Dopamine is a beta 1 receptor agonist used for short-term treatment of bradycardia. It increases heart rate and contractility.

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IV Dobutamine in bradycardia

Dobutamine is a selective beta 1 receptor agonist used for short-term treatment of bradycardia. It is more selective for beta 1 than beta 2, making it more specific for heart stimulation.

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Warfarin Alternatives

Drugs used for anticoagulation when warfarin is not suitable, such as Xaban (direct Factor X inhibitor) and Dabigatran (direct thrombin inhibitor).

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Heparins

Anticoagulants that work by binding paradoxical clotting factors for warfarin treatment, activating antithrombin III, and removing clotting factors.

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Direct inhibitors of Factor X

Drugs like Xaban directly inhibit Factor X, preventing the clotting cascade and reducing thromboembolic risk.

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Direct thrombin inhibitor

Drugs like Dabigatran directly inhibit thrombin, preventing the formation of fibrin clots and reducing thromboembolic events.

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Antiplatelet drugs (P2Y12 Antagonist)

Drugs that block platelet activation and aggregation, reducing the formation of blood clots. These include Clopidogrel, Prasugrel, and Ticagrelor.

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Class 1b Antiarrhythmics

Antiarrhythmic drugs that effectively treat very fast heart rates, particularly ventricular tachycardia, but have minimal effect on atrial fibrillation or atrial tachycardia. They work primarily on the rapid dissociation phase of the action potential.

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Lidocaine

A Class 1b antiarrhythmic drug administered intravenously, used to treat ventricular tachycardia. It has minimal impact on slower rhythms like atrial fibrillation.

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Class 1c Antiarrhythmics

Potent antiarrhythmic drugs effective for both atrial and ventricular tachycardias. They have a strong negative inotropic effect and are associated with the risk of myocardial infarction if used after a heart attack.

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Flecainide

A Class 1c antiarrhythmic drug that effectively treats a variety of tachycardias but increases the risk of myocardial infarction if used after a heart attack.

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Propafenone

A Class 1c antiarrhythmic drug that effectively treats atrial and ventricular tachycardias. It also has beta-blocker effects.

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Class II Antiarrhythmics

Antiarrhythmic drugs that block calcium channels and typically end in 'ol'. They prolong the phase 4 depolarization in the AV node, effectively reduce arrhythmias, and are used post-MI.

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Solatol

A Class II antiarrhythmic drug with both Class II and Class III activity. It prolongs the action potential duration and is used post-MI.

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Class III Antiarrhythmics

Antiarrhythmic drugs that block potassium channels, extending the effective refractory period and slowing the heart rate. They are effective for slowing heart rate and have a unique mechanism of action.

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Amiodarone

A Class III antiarrhythmic drug that blocks potassium channels, effectively slows heart rate, and has additional Class I and IV activities. It is extremely lipophilic, leading to possible adverse effects.

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Class IV Antiarrhythmics

Antiarrhythmic drugs that block calcium channels, reducing heart contractility and slowing heart rate. They are used for a variety of arrhythmias and can also be used for other cardiovascular conditions.

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Study Notes

Drugs for Tachycardia

  • Class 1a drugs (discontinued): Quinidine, Procainamide, Disopyramide

    • Mechanism of action: Slows down myocardial depolarization during phase 1
    • Use: Atrial/ventricular tachycardia
    • Contraindications: Avoid in people with hypotension and low ventricular output
    • Adverse effects: High risk of Torsades de pointes (TdP), heart attack, anti-cholinergic side effects (urinary retention, urinary hypertension). Negative inotropic effect (reduces contractility)

  • Class 1b drugs: Lidocaine

    • Mechanism of action: Blocks sodium channels
    • Use: Effective at very fast heart rates (ventricular tachycardia)
    • Administered: IV
    • Adverse effects: Low effect on atrial tachycardia

Drugs for Tachycardia (Class 1c)

  • Flecainide:

    • Mechanism of action: Rapid dissociation
    • Use: Atrial fibrillation and ventricular tachycardia
    • Administered: Orally
    • Adverse effects: Low effect at atrial tachycardia, potentially harmful in myocardial infarction

  • Tocainide (discontinued):

    • Mechanism of action: Rapid dissociation
    • Use: Ventricular tachycardia, atrial fibrillation
    • Administered: Orally
    • Adverse effects: Low effect on atrial tachycardia

  • Propafenone:

    • Mechanism of action: Blocks Ca2+ channels
    • Use: Atrial fibrillation and ventricular tachycardia
    • Administered: Orally
    • Adverse effects: Potentially harmful in myocardial infarction (MI)

Class II drugs

  • Mechanism of Action: Blocks Ca2+ channels.
  • Examples: Atenolol, Metoprolol, Propanolol
  • Use: Reduce arrhythmias, given post-MI
  • Contraindications: Asthma
  • Adverse effects: Hypotension, fatigue, dizziness, peripheral vasoconstriction

Class III drugs

  • Mechanism of Action: Block K+ channels, extending both nodal and effective refractory periods.
  • Examples: Amiodarone
  • Use: Effective for slow heart rates, atrial fibrillation and ventricular tachycardia.
  • Contraindications: Bradycardia
  • Adverse Effects: Extremely toxic, thyroid dysfunction, Torsades de Pointes (TdP)

Class IV drugs

  • Mechanism of Action: Blocks Ca2+ (L-type) channels, decreasing nodal AP amplitude and increasing nodal AP duration.
  • Examples: Verapamil, Diltiazem.
  • Use: Atrial fibrillation, paroxysmal supraventricular tachycardia, dilation of blood vessels.
  • Contraindications: Ventricular tachycardia
  • Adverse effects: Hypotension, dizziness, edema, constipation, Due to: shortens myocyte AP

Drugs for Bradycardia

  • IV Atropine: Non-specific muscarinic antagonist
  • IV Adrenaline: Non-specific adrenergic agonist, primarily acts on Beta-1 receptors.
  • IV Dopamine: Acts on Beta-1 receptors in the heart.
  • IV Dobutamine: Slightly selective for Beta-1 receptors over Beta-2.

Cardiac Drugs (Angina)

  • Glyceryl Trinitrate(GTN): Reduces O2 via vasodilation. Used for acute angina. Avoid liver metabolism tablet
  • Beta Blockers (e.g., Propranolol): Inhibits adrenaline & sympathetic nervous system on heart. Improves left ventricular end-diastolic volume and decreases ventricular mass. Used for treating angina.

Other Beta-Blockers

  • Atenolol: 30-fold selectivity, water soluble.
  • Bisoprolol: 75-fold selectivity, water soluble.

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Description

This quiz covers different classes of drugs used to treat tachycardia, including the mechanisms of action, uses, contraindications, and adverse effects of Class 1a, 1b, and 1c drugs. It is essential for understanding pharmacological approaches to tachycardia management.

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