Cardioactive Drugs Overview

Classification of Cardioactive Drugs

• Class I: Rapid sodium channel blockers (e.g., Quinidine, Procainamide, Lidocaine)
• Class II: Beta receptor blockers (e.g., Propranolol)
• Class III: Potassium channel blockers (e.g., Amiodarone)
• Class IV: Calcium channel blockers (e.g., Verapamil)
• Digoxin: Cardiac glycoside for atrial arrhythmia and CHF

Digoxin

• Therapeutic range: 0.5-2 ng/mL; toxic level: >2 ng/mL
• Inhibits Na-K-ATPase in high doses, causing decreased K+ and Mg2+, and increased Ca2+ for increased cardiac contractility
• Absorbed variably through the gastrointestinal tract (GIT); renal clearance affects serum concentration
• 25% protein-bound; free form sequestered into muscle cells
• Timing of blood sample critical for accurate drug level interpretation
• Half-life in adults: 38 hours; peak serum levels occur 8 hours post-oral dose
• Toxic effects include nausea, vomiting, visual disturbances, and AV node blockage

Lidocaine (Xylocaine)

• Used for treating ventricular arrhythmia, particularly in acute myocardial infarction
• Administered via continuous IV infusion following a loading dose; cannot be given orally due to hepatic extraction
• Protein-bound; primarily eliminated through hepatic metabolism
• Therapeutic level: 1.5-4.0 µg/mL; toxicity begins at >4.0 µg/mL
• Toxic effects include CNS depression, seizures, CHF, and heart block

Quinidine

• Naturally occurring drug for arrhythmia management; 85% protein-bound
• Delivered orally; common formulations are quinidine sulfate and gluconate
• Peak serum levels: 2 hours for sulfate, 4-5 hours for gluconate
• Therapeutic level: 2.3-5 µg/mL; toxicity level: >5 µg/mL
• Toxic effects include cinchonism, blood dyscrasia, and hepatitis

Procainamide (Pronestyl)

• Treats ventricular arrhythmia with rapid and complete GIT absorption
• 20% protein-bound; elimination through renal filtration and hepatic metabolism
• Peak serum level occurs one hour after dosing; therapeutic level: 4-10 µg/mL; toxic level: >12 µg/mL
• Toxic effects include reversible lupus-like syndrome, nephrotic syndrome, and urticaria

Disopyramide

• Substituted for quinidine in treating cardiac arrhythmias
• Given orally with complete and rapid absorption; shares anticholinergic effects (e.g., dry mouth, constipation)
• Therapeutic level: 3-5 µg/mL; toxic level: >10 µg/mL
• Toxic effects include bradycardia and AV node blockage

Propranolol

• A beta-receptor blocker for angina pectoris, hypertension, coronary artery disease, and thyrotoxicosis treatment
• Suppresses conversion of T4 to T3
• Therapeutic range: 50-100 ng/mL
• Toxic effects include bradycardia, arterial insufficiency (Raynaud's type), platelet disorders, and pharyngitis

Amiodarone (Cordarone)

• Blocks potassium channels; treats ventricular arrhythmias
• Iodine-containing drug; can induce hyperthyroidism or hypothyroidism
• Therapeutic level: 1.0-2.5 µg/mL; toxicity >2.5 µg/mL
• Toxic effects include bradycardia, hepatitis, photodermatitis, and thyroid dysfunction

Verapamil

• Used for angina, hypertension, and supraventricular arrhythmias
• Therapeutic range: 80-400 ng/mL
• Toxic effects may include hypotension, peripheral edema, and ventricular fibrillation

This quiz covers the classification and usage of cardioactive drugs, including their roles in treating arrhythmias and congestive heart failure (CHF). You will learn about the different classes of drugs and specific examples such as Quinidine and Amiodarone. Test your knowledge on these crucial pharmaceuticals and their therapeutic actions.