Y1S2 004 I Pharmacology Cardiovascular: Medications and Mechanisms

Cardiovascular Drugs

Beta Blockers - Propranolol

• Non-selective β-antagonist, used to treat angina, hypertension, arrhythmias, and glaucoma
• Inhibits contraction of the heart by blocking β1 receptors, reducing heart rate and force of contraction
• Adverse effects: bronchi-constriction, cardiac failure, fatigue, and depression
• Route of administration: oral, with a half-life of 4 hours and high first-pass metabolism

Vasodilators - Nitroglycerin

• Dilates blood vessels, reducing blood pressure and workload on the heart
• Converted to nitric oxide (NO) by mitochondrial aldehyde dehydrogenase (MtALDH)
• Route of administration: intravenous, sublingual, with a peak concentration time of approximately 4.4 minutes
• Adverse effects: hypotension, vertigo, flushed skin, diaphoresis, fever, syncope, dyspnea, and bradycardia

Cardiac Glycosides - Digitalis (Digoxin)

• Increases force of contraction of the heart, used to treat congestive cardiac failure (CCF)
• Extracted from the foxglove plant (Digitalis spp.), with digoxin being the main drug in this class
• Acts on the heart, increasing intracellular Ca²⁺ concentrations, which leads to increased force of contraction
• Adverse effects: arrhythmia (tachycardia, atrioventricular block), hypokalemia, abdominal discomfort, nausea, and vomiting
• Route of administration: oral or intravenous, with a half-life of 36-40 hours

Antiplatelets - Aspirin

• Prevents clotting of blood by inhibiting the synthesis of thromboxane A2 (TXA2) in platelets
• Irreversible inhibition of cyclooxygenase (COX) enzyme, specifically COX 1 in platelets
• Route of administration: oral, with a dose of 160-320 mg/d, and a duration of 7-9 days
• Adverse effects: GIT irritation, and used at low doses to prevent platelet aggregation

Anticoagulants - Heparin and Low Molecular Weight Heparin (LMWH)

• Prevent clotting of blood by inactivating clotting factors IIa, IXa, Xa, XIa, and XIIa
• Inhibit coagulation cascade, preventing fibrin formation and blood clotting
• Route of administration: intravenous, subcutaneous, with a low therapeutic index
• Adverse effects: osteoporosis, hyperkalemia, hypersensitivity reactions, and heparin-induced thrombocytopenia

Anticoagulants - Warfarin

• Inhibits blood clot formation by preventing the synthesis of clotting factors II, VII, IX, and X
• Structurally related to vitamin K, with a slow onset of 48 hours and a peak anticoagulant effect at 72-96 hours
• Route of administration: oral, with a half-life of 25-60 hours, and a high plasma protein binding of 99%
• Adverse effects: diarrhea, bleeding, warfarin-induced skin necrosis, and a low therapeutic index
• Monitored using prothrombin time (PT) and international normalized ratio (INR)