Drugs Acting on the Cardiovascular System
Medicines affecting the cardiovascular system are used to control heart rhythm, reduce blood pressure, prevent chest pain, and manage heart failure. They act on the heart muscles, blood vessels, or electrical conduction system to restore normal function and reduce cardiac stress.
Anti-Arrhythmic Drugs
Heart rhythm disorders, known as arrhythmias, occur when the heartbeat becomes abnormally fast (tachycardia), slow (bradycardia), or irregular. Some arrhythmias are harmless, while others may cause chest discomfort, fainting, shortness of breath, or increase the risk of stroke and cardiac arrest.
Drugs used to restore a normal heart rhythm are known as anti-arrhythmic agents.
Classification of Anti-Arrhythmic Drugs
- Class I – Sodium Channel Blockers: Quinidine, Procainamide, Disopyramide, Lignocaine, Mexiletine, Phenytoin, Flecainide, Propafenone
- Class II – Beta Blockers: Propranolol, Esmolol, Sotalol
- Class III – Agents Prolonging Action Potential: Amiodarone, Dofetilide, Bretylium
- Class IV – Calcium Channel Blockers: Verapamil, Diltiazem
Examples of Anti-Arrhythmic Drugs
Common medicines include Quinidine, Procainamide, Verapamil, Phenytoin, Lidocaine, Lorcainide, Amiodarone, and Sotalol.
Quinidine Sulphate
Quinidine is a Class IA anti-arrhythmic drug that slows electrical conduction through the heart by blocking sodium entry into cardiac cells. This action reduces abnormal impulses and increases the refractory period.
Uses
- Treatment of life-threatening ventricular arrhythmias
- Also used intravenously for Plasmodium falciparum malaria
Procainamide Hydrochloride
Procainamide blocks open sodium channels, reducing excitability of cardiac tissue and slowing impulse conduction. It is effective against atrial and ventricular arrhythmias.
Uses
- Ventricular tachycardia and ventricular ectopy
- Atrial fibrillation and supraventricular tachycardia
Verapamil
Verapamil is a calcium channel blocker used to reduce heart rate and blood pressure by affecting calcium movement in cardiac and vascular cells.
Uses
- Supraventricular tachyarrhythmias
- Hypertension and angina pectoris
- Prevention of cluster headaches
Phenytoin Sodium
Phenytoin stabilizes sodium channels and increases the refractory period, making it useful in arrhythmias caused by digitalis toxicity.
Uses
- Ventricular tachycardia
- Control of seizure disorders
Lidocaine Hydrochloride
Lidocaine blocks fast sodium channels, suppresses abnormal impulses, and is especially effective in ventricular arrhythmias.
Uses
- Treatment of ventricular arrhythmias
- Local and regional anesthesia
Amiodarone
Amiodarone prolongs cardiac action potential and refractory period, reducing abnormal automaticity and conduction.
Uses
- Recurrent ventricular tachycardia and ventricular fibrillation
- Used when other anti-arrhythmic drugs fail
Sotalol
Sotalol has beta-blocking and potassium channel blocking actions, making it effective in maintaining normal sinus rhythm.
Uses
- Atrial fibrillation and flutter prevention
- Treatment of life-threatening ventricular arrhythmias
Anti-Hypertensive Agents
Hypertension is persistent elevation in blood pressure that increases the risk of heart failure, stroke, and kidney damage. Anti-hypertensive drugs reduce systemic pressure by acting on blood vessels, kidneys, or the heart.
Classification of Anti-Hypertensive Drugs
- Diuretics: Hydrochlorothiazide, Furosemide, Spironolactone
- ACE Inhibitors: Captopril, Lisinopril, Ramipril
- Angiotensin II Blockers: Losartan, Valsartan, Irbesartan
- Adrenergic Drugs: Clonidine, Methyldopa, Propranolol
- Calcium Channel Blockers: Verapamil, Amlodipine, Nifedipine
- Vasodilators: Hydralazine, Minoxidil, Sodium nitroprusside
Anti-Anginal Agents
Angina pectoris causes chest pain due to reduced oxygen supply to the heart. Anti-anginal drugs restore balance between oxygen supply and demand in heart muscles.
Example: Isosorbide Dinitrate
Isosorbide dinitrate releases nitric oxide, which relaxes smooth muscles and causes vasodilation. This improves blood flow through coronary vessels and reduces cardiac workload.
Uses
- Prevention and treatment of angina pectoris
- Management of congestive heart failure
- Relief of esophageal spasms
