Cardiac Drugs Mechanisms of Action

Anti-Angina Medications

• Calcium channel blockers relax coronary and peripheral arteries, reducing myocardial oxygen demand and improving blood flow to the heart.
• Ranolazine inhibits the late sodium current in cardiac cells, reducing intracellular calcium overload and myocardial ischemia.
• Examples of anti-angina medications include nitroglycerin, beta-blockers (e.g., metoprolol, atenolol), calcium channel blockers (e.g., amlodipine, nifedipine), ranolazine (Ranexa), and isosorbide dinitrate.

Side Effects of Anti-Angina Medications

• Common side effects include headache, dizziness, flushing, fatigue, and nausea.
• Adverse effects include hypotension, reflex tachycardia, peripheral edema, and exacerbation of heart failure symptoms.

Cardiotonic/Inotropic Drugs

• These medications are used to improve the strength and efficiency of the heart's contractions, particularly in heart failure.
• They work by increasing calcium levels in heart muscle cells, enhancing contraction.
• Examples include digoxin and certain phosphodiesterase inhibitors (e.g., milrinone).

Mechanism of Action of Cardiotonic Drugs

• Cardiotonic drugs aim to enhance the strength and efficiency of cardiac contraction, particularly in heart failure.
• They primarily increase intracellular calcium levels or sensitize contractile proteins in cardiac muscle cells.

Examples of Cardiotonic/Inotropic Drugs

• Digoxin inhibits the sodium-potassium ATPase pump, leading to increased intracellular calcium and enhanced myocardial contractility.
• Dobutamine stimulates beta-1 adrenergic receptors, increasing intracellular cyclic AMP levels and enhancing myocardial contractility.
• Milrinone inhibits phosphodiesterase III, leading to increased intracellular cyclic AMP levels, which enhances myocardial contractility and vasodilation.
• Levosimendan sensitizes cardiac myofilaments to calcium, increasing myocardial contractility without increasing intracellular calcium levels.

Side Effects of Cardiotonic/Inotropic Drugs

• Common side effects include nausea, vomiting, headache, dizziness, and visual disturbances.
• Adverse effects include cardiac arrhythmias, hypotension, myocardial ischemia, thrombocytopenia, and electrolyte disturbances.

Antiarrhythmic Drugs

• Class II antiarrhythmics (beta-blockers) like metoprolol and propranolol decrease sympathetic activity, reducing heart rate and contractility.
• Class III antiarrhythmics (potassium channel blockers) like amiodarone and sotalol prolong the action potential duration, delaying repolarization.
• Class IV antiarrhythmics (calcium channel blockers) like verapamil and diltiazem inhibit calcium influx into cardiac cells, slowing conduction through the AV node and reducing heart rate.

Examples of Antiarrhythmic Drugs

• Beta-blockers (e.g., metoprolol, propranolol)
• Calcium channel blockers (e.g., verapamil, diltiazem)
• Sodium channel blockers (e.g., flecainide, propafenone)
• Potassium channel blockers (e.g., amiodarone, sotalol)
• Digoxin

Side Effects of Antiarrhythmic Drugs

• Common side effects include fatigue, dizziness, nausea, constipation or diarrhea, and blurred vision.
• Adverse effects include proarrhythmia, hypotension, bradycardia, QT prolongation, and liver toxicity.

Antihyperlipidemics

• These drugs are used to lower elevated levels of lipids (fats) in the blood, particularly cholesterol and triglycerides.
• High levels of these lipids are associated with an increased risk of cardiovascular diseases such as heart attacks and strokes.