Drugs Affecting the Cardiovascular System Flashcards
What are cardiovascular drugs and their classification?
Cardiovascular drugs are diverse group of pharmacological agents used to treat various conditions related to the heart and blood vessels.
These drugs can be classified based on their mechanism of action and therapeutic use which include:
1. Antihypertensive
2. Antiarrhythmic
3. Inotropes
4. Vasodilators
5. Anticoagulants
6. Antiplatelet Agents
7. Cholesterol-Lowering Drugs.
What are Antiarrhythmic drugs and their classification?
Antiarrhythmic drugs are used to treat abnormal heart rhythms (arrhythmias). They work by modifying the electrical impulses that regulate the heartbeat, helping to restore a normal rhythm.
These drugs are classified into several classes based on their mechanisms of action which include: Class I: Sodium Channel Blockers, Class Ib, Class Ic.
Class II: Beta-Adrenergic Blockers, Class III: Potassium Channel Blockers, Class IV: Calcium Channel Blockers
What are Class I: Sodium Channel Blockers?
These drugs block sodium channels, which are involved in the depolarization phase of the cardiac action potential. They are further divided into three subclasses:
Class Ia: Moderate sodium channel blockade, which prolongs the action potential duration.
Examples: Quinidine: Used for atrial fibrillation and ventricular arrhythmias (side effect is cinchonism)
Procainamide: Used for ventricular arrhythmias and atrial fibrillation.
Disopyramide: Used for ventricular arrhythmias, but has significant anticholinergic effects.
Class Ib
Mechanism: Weak sodium channel blockade, primarily affects ischemic or depolarized cardiac tissue, and shortens the action potential duration.
Examples: Lidocaine: Primarily used for ventricular arrhythmias, especially post-myocardial infarction.
Mexiletine: Similar to lidocaine, used for chronic ventricular arrhythmias.
Class Ic:
Mechanism: Strong sodium channel blockade, markedly slows conduction velocity without significantly affecting the action potential duration.
Examples: Flecainide; Used for atrial fibrillation and ventricular arrhythmias.
Propafenone; Used for atrial fibrillation and ventricular arrhythmias; also has beta-blocking activity.
Class II: Beta-Adrenergic Blockers
These drugs block beta-adrenergic receptors, which reduces sympathetic nervous system activity and slows down the heart rate.
Examples: Metoprolol; used for atrial fibrillation, atrial flutter, and ventricular arrhythmias.
Atenolol: Used for various arrhythmias, including atrial fibrillation.
Propranolol: Used for both atrial and ventricular arrhythmias, and has additional uses in reducing anxiety and preventing migraines.
Class III: Potassium Channel Blockers examples and side effects
These drugs block potassium channels, which prolong the repolarization phase of the cardiac action potential, thus prolonging the refractory period.
Examples: Amiodarone; A broad-spectrum antiarrhythmic used for both atrial and ventricular arrhythmias, including atrial fibrillation and ventricular tachycardia. It can cause a variety of side effects, including thyroid and lung issues.
Sotalol: Used for atrial fibrillation and ventricular arrhythmias. It also prolongs the QT interval, which can lead to torsades de pointes.(a form of polymorphic ventricular tachycardia)
Dofetilide: Used for atrial fibrillation and flutter, also prolongs the QT interval.
Class IV: Calcium Channel Blockers & other anti arrhythmic agents
These drugs block calcium channels, which affects the conduction through the atrioventricular (AV) node and reduces heart rate.
Examples: Verapamil; Used for atrial fibrillation, atrial flutter, and certain types of supraventricular tachycardias. It slows AV nodal conduction and can reduce heart rate.
Diltiazem: Similar to verapamil, used for atrial fibrillation and supraventricular tachycardias.
Nifedipine
Other Antiarrhythmic Agents: Adenosine; Used for the rapid termination of certain types of supraventricular tachycardias (SVTs) by briefly blocking AV node conduction.
Digoxin: Used primarily for atrial fibrillation and flutter, particularly in patients with heart failure. It increases vagal tone, which can slow AV nodal conduction.
What are Antianginal Drugs?
How are nitrates antianginal?
Antianginal drugs are used to relieve or prevent angina pectoris, which is chest pain or discomfort caused by inadequate blood supply to the heart muscle. They work by improving blood flow to the heart or reducing the heart’s oxygen demand. Examples include;
Nitrates: Nitrates are used to relieve angina by dilating blood vessels, which reduces the heart’s workload and improves blood flow to the heart muscle (Short- Acting Nitrates- Nitroglycerin, Isosorbide dinitrate; Long-Acting Nitrates: Isosorbide mononitrate).
Nitrates are converted to nitric oxide (NO), which relaxes smooth muscle cells in blood vessels, leading to vasodilation. This reduces preload (venous return) and, consequently, myocardial oxygen demand.
Considerations: Tolerance can develop with prolonged use, so nitrates should be used with a nitrate-free interval. Side effects include headaches, dizziness, and hypotension.
Antihypertensive Drugs and their classification
Antihypertensive drugs are used to manage high blood pressure (hypertension) and reduce the risk of complications such as heart attack, stroke, and kidney damage.
These medications work through various mechanisms to lower blood pressure,
Major classes of antihypertensive drugs include:
* Diuretics, (e.g., hydrochlorothiazide, furosemide)
* ACE inhibitors (e.g., enalapril, lisinopril).
* Angiotensin II receptor blockers (ARBs) (e.g., losartan, valsartan),
* Beta-blockers (e.g., carvedilol, metoprolol)
* Alpha blockers eg. Prazosin, Terazosin, Doxazosin Phentolamine, Phenoxybenzamine
* Direct renin inhibitors e.g Aliskren
* Calcium channel blockers (e.g. amlodipine, nifedipine)
* Vasodilators e.g hydralazine, minoxidil
Diuretics, types and examples
Diuretics help reduce blood pressure by eliminating excess sodium and water from the body, thus decreasing blood volume.
Classes include:
- Thiazide Diuretics: Act on the distal convoluted tubule of the nephron to inhibit sodium reabsorption (Hydrochlorothiazide, chlorthalidone).
Contraindication: not given to pregnant women
Indications: Often used as first-line treatment for hypertension, particularly effective in uncomplicated hypertension.
- Loop Diuretics: Act on the ascending limb of the loop of Henle to inhibit sodium reabsorption (Furosemide (Lasix), bumetanide)
Indications: Used in cases of heart failure or renal impairment where more potent diuresis is needed.
- Potassium-Sparing Diuretics: Act on the distal part of the nephron to inhibit sodium reabsorption while retaining potassium (Spironolactone, eplerenone)
Indications: Often used in combination with thiazide diuretics to prevent potassium loss
ACE inhibitors
ACE inhibitors block the enzyme angiotensin-converting enzyme (ACE), which reduces the production of angiotensin II, a potent vasoconstrictor.
Examples: Enalapril; Reduces blood pressure by decreasing angiotensin II levels and reducing aldosterone secretion.
Lisinopril: Similar to enalapril, often used for hypertension and heart failure.
Ramipril: Provides cardiovascular protection and is used in various cardiovascular conditions.
Angiotensin II Receptor Blockers (ARBs)
ARBs block the receptors for angiotensin II, preventing its vasoconstrictive effects.
Examples: Losartan; Blocks angiotensin II receptors to reduce blood pressure and improve kidney function.
Valsartan: Similar to losartan, used for hypertension and heart failure.
Candesartan: Effective in reducing blood pressure and providing renal protection.
Alpha-blockers
Characteristic use in males
Alpha-blockers reduce blood pressure by blocking alpha-adrenergic receptors, leading to vasodilation.
Examples:
Doxazosin; Used for hypertension and benign prostatic hyperplasia (BPH).
Prazosin: Effective for hypertension and post-traumatic stress disorder (PTSD)-related nightmares.
Discuss Anticoagulants
(Particularly vitamin k antagonists and warfarin)
Anticoagulants are medications that help prevent blood clots from forming or growing larger. They are used to treat or prevent conditions such as deep vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation, and to reduce the risk of stroke or heart attack. Examples include;
Vitamin K Antagonists: These drugs inhibit the vitamin K epoxide reductase enzyme, which is necessary for the synthesis of vitamin K-dependent clotting factors (Factors II, VII, IX, and X) in the liver. By reducing these factors, they slow down the blood clotting process.
Examples: Warfarin (Coumadin); One of the most commonly used vitamin K antagonists. It requires regular monitoring of the INR (International Normalized Ratio) to ensure therapeutic levels and prevent bleeding complications.
Considerations: Warfarin’s effect can be influenced by diet (e.g., foods high in vitamin K) and other medications. It has a delayed onset and requires regular blood tests to monitor its effect.
