Pharmacology of Cardiovascular Drugs

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Questions and Answers

Which of the following drugs can be used to treat hypertension?

Anti-arrhythmic agents

Calcium channel blockers (correct)

Anticoagulants

Beta-blockers (correct)

What is a common cause of arrhythmias?

Decreased heart rate variability

High levels of potassium

Ectopic pacemaker activity (correct)

Increased vagal tone

What condition is characterized by a prolonged QT interval?

After-depolarizations (correct)

Bradycardia

Tachycardia

Atrial flutter

What is the effect of drugs that block voltage-sensitive sodium channels?

Stabilize cardiac membranes Signup and view all the answers

Which type of arrhythmia involves multiple small re-entry loops?

Atrial fibrillation Signup and view all the answers

What mechanism allows for the development of a circus of excitation in arrhythmias?

Unidirectional conduction block Signup and view all the answers

What happens during ventricular tachycardia?

The heart beats too quickly due to abnormal pacemaker activity Signup and view all the answers

Which factor does NOT influence blood volume in the cardiovascular system?

Coronary artery blood flow Signup and view all the answers

What is the primary action of dobutamine?

Acts on β1 receptors Signup and view all the answers

Which of the following is NOT a use for dobutamine?

Hypertension treatment Signup and view all the answers

What is a primary mechanism by which ACE-inhibitors aid in heart failure treatment?

Prevent Na+ and water re-absorption Signup and view all the answers

Which class of drugs helps reduce the preload on the heart?

Diuretics Signup and view all the answers

What condition leads to angina due to inadequate oxygen supply?

Coronary artery narrowing Signup and view all the answers

Which of these is a primary method to improve blood supply to the heart?

Calcium channel antagonists Signup and view all the answers

What substance is released when organic nitrates react with thiols in the vascular smooth muscle?

Nitric Oxide (NO) Signup and view all the answers

What is the ultimate effect of Nitric Oxide on vascular smooth muscle cells?

Muscle relaxation Signup and view all the answers

What is the primary mechanism by which lidocaine exerts its effects on the heart?

Blocking voltage-gated Na+ channels in open or inactive states Signup and view all the answers

Beta-blockers are beneficial after a myocardial infarction primarily because they...

Block β1-adrenoreceptors, reducing O2 demand Signup and view all the answers

Which class of anti-arrhythmic drugs is known for prolonging the absolute refractory period?

Class III Signup and view all the answers

Amiodarone is unique among class III anti-arrhythmics because it also...

Has additional pharmacological actions beyond K+ channel blocking Signup and view all the answers

What effect does verapamil, a class IV drug, have on the heart?

Decreases the force of contraction Signup and view all the answers

Which of the following is NOT a common target of anti-arrhythmic drugs?

Chloride channels Signup and view all the answers

How does adenosine function as an anti-arrhythmic agent?

It enhances potassium conductance at the AV node Signup and view all the answers

The term 'inotropic drug' refers to drugs that impact which aspect of cardiac function?

Force of contraction Signup and view all the answers

After a myocardial infarction, which class of drug is NOT typically used prophylactically?

Lidocaine Signup and view all the answers

What is a significant risk associated with drugs that block potassium channels?

Pro-arrhythmia due to prolonged action potential Signup and view all the answers

What is the primary effect of negatively inotropic drugs on the heart?

Reduce workload of the heart Signup and view all the answers

Which of the following is an example of a positive inotropic drug?

Dobutamine Signup and view all the answers

What is the effect of cardiac glycosides on intracellular calcium concentration?

Increase intracellular calcium levels Signup and view all the answers

How do cardiac glycosides influence heart rate?

Slow the heart rate by increasing vagal activity Signup and view all the answers

What condition is characterized by the heart's failure to provide sufficient output to meet the body's requirements?

Heart failure Signup and view all the answers

Which of the following is NOT a feature of heart failure?

Increased cardiac output Signup and view all the answers

What action does digoxin take on the Na+/K+ ATPase?

Inhibits its function Signup and view all the answers

Which type of drug would be used to increase cardiac output in a patient experiencing cardiogenic shock?

Positive inotropic drugs Signup and view all the answers

The mechanism by which cardiac glycosides increase the force of contraction involves which exchanger?

Na+/Ca2+ exchanger Signup and view all the answers

What physiological effect do β-blockers primarily have?

Reduce heart rate and workload Signup and view all the answers

What is the primary action of venodilation on the heart?

Reduces workload and lowers O2 demand Signup and view all the answers

Which condition does NOT carry an increased risk of thrombus formation?

Hypertension Signup and view all the answers

What is the mechanism of action of warfarin?

Antagonises the action of vitamin K Signup and view all the answers

How do organic nitrates primarily affect collateral arteries?

Dilate collateral arteries to increase blood flow Signup and view all the answers

Which of the following is NOT an anti-platelet drug?

Warfarin Signup and view all the answers

What is the effect of blood volume increase associated with hypertension?

Increased blood pressure Signup and view all the answers

Which form of heparin is administered intravenously for acute treatments?

Heparin Signup and view all the answers

Which best describes the secondary action of nitrates on the coronary arteries?

Improving oxygen delivery to ischaemic myocardium Signup and view all the answers

Study Notes

Action of Drugs on the Cardiovascular System

Cardiovascular drugs treat various conditions, including arrhythmias, heart failure, blood clotting disorders, ischemic heart diseases, and hypertension.
Drugs can alter heart rate, rhythm, myocardial contractility, peripheral resistance, blood volume, and coronary artery blood flow.
Some drugs affect multiple sites.

Types of Arrhythmias

Arrhythmias are disturbances of cardiac rhythm.
Tachycardia involves an abnormally fast heart rate, including ventricular and supraventricular tachycardias.
Bradycardia is an abnormally slow heart rate.
Atrial flutter and fibrillation, and ventricular fibrillation are further examples of arrhythmias..

Causes of Arrhythmias

Ectopic pacemaker activity: Damaged myocardial areas fire spontaneously.
Latent pacemaker regions, activated due to ischemia (reduced blood flow).
Abnormal depolarizations after action potential, potentially due to high intracellular calcium.
Longer action potentials result in longer QT intervals.
Re-entry loop: Incomplete conduction damage allows impulses to circle in a damaged area.

Anti-Arrhythmic Drugs

Four basic classes exist:
- Drugs that block voltage-sensitive sodium channels (e.g., lidocaine).
- Antagonists of β-adrenoreceptors (e.g., propranolol, atenolol).
- Drugs that block potassium channels (e.g., amiodarone).
- Drugs that block calcium channels (e.g., verapamil).
Lidocaine is used to manage ventricular tachycardia following myocardial infarction (MI).
Beta blockers reduce sympathetic activity, limiting arrhythmias after MI and decreasing oxygen demand.
Amiodarone, a type III anti-arrhythmic, also has other actions besides blocking potassium channels and is used for Wolff-Parkinson-White syndrome tachycardias.
Verapamil is a calcium channel blocker that slows AV nodal conduction and reduces heart contractility.
Adenosine, used intravenously to treat arrhythmias, doesn't fall into typical anti-arrhythmic classes.

Inotropic Drugs

Inotropic drugs affect the force of heart contraction.
Negatively inotropic drugs reduce workload, useful after a myocardial infarction to limit damage. Beta-blockers are one example.
Positively inotropic drugs increase the force of contraction needed to improve cardiac function for conditions such as cardiogenic shock or acute heart failure. Examples include dobutamine and isoprenaline.

Heart Failure

Heart failure occurs when the heart cannot meet the body's blood flow demands.
Features include reduced force of contraction, reduced cardiac output, reduced tissue perfusion, and edema.
Positive inotropic drugs (e.g., cardiac glycosides, dobutamine, dopamine, isoprenaline) increase cardiac output.
Drugs that reduce workload (e.g., ACE inhibitors, diuretics) are also important in treating heart failure.

Cardiac Glycosides

Cardiac glycosides, such as digoxin, have been used for over 200 years to treat heart failure.
Digoxin improves symptoms but doesn't always improve long-term outcomes.
It's extracted from foxglove plants and works by inhibiting the Na+/K+ ATPase pump.
This increases intracellular calcium, which bolsters cardiac contraction force.
Cardiac glycosides also slow the heart rate via vagal activity.

Drugs for Myocardial Ischemia (Angina)

Angina happens when blood flow to the heart isn't sufficient to meet the oxygen demands, causing ischemia and pain, typically during exertion.
Treatments reduce workload, use beta-blockers, calcium channel antagonists, and organic nitrates to improve blood flow.

Thrombosis

Certain conditions—including atrial fibrillation, acute myocardial infarction, and mechanical heart valves—increase thrombus formation risk.
Anticoagulants like heparin (short-term) and warfarin (long-term) prevent clots.
Anti-platelet drugs like aspirin, dipyridamole, and clopidogrel are often used after an MI or in patients at high risk for MI

Hypertension

Hypertension (high blood pressure) usually involves increased blood volume due to sodium and water retention by kidneys.
Treatments include diuretics, ACE inhibitors, beta-blockers, calcium channel blockers, and alpha-1-adrenceptor antagonists. These often cause vasodilation.

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Description

This quiz explores various pharmacological concepts related to cardiovascular drugs used for treating conditions such as hypertension and arrhythmias. Test your knowledge on drug mechanisms, conditions related to the cardiovascular system, and specific drug actions like those of dobutamine and ACE-inhibitors.