Antianginal agents are medicines used to relieve and prevent angina pectoris — a type of chest pain caused by reduced blood supply to the heart. Vasodilators are a major class of these drugs because they relax blood vessels, improve oxygen supply, and reduce the workload on the heart.
What Is Angina?
Angina occurs when the heart muscle does not receive enough oxygen-rich blood. It is commonly caused by:
- Coronary artery disease (narrowing of heart vessels)
- Stress or exertion
- Increased oxygen demand of the heart
Types of Angina
- Stable angina – Triggered by exercise or stress
- Unstable angina – Sudden, unpredictable, and more severe
- Variant (Prinzmetal’s) angina – Caused by coronary artery spasm
Goals of Antianginal Therapy
- Reduce heart oxygen demand
- Increase blood flow to the heart
- Prevent or relieve chest pain
Classification of Antianginal Agents
1. Nitrates
- Nitroglycerin
- Isosorbide dinitrate
- Isosorbide mononitrate
2. Beta Blockers
- Atenolol
- Metoprolol
- Propranolol
3. Calcium Channel Blockers
- Verapamil
- Diltiazem
- Amlodipine
4. Potassium Channel Activators
- Nicorandil
5. Miscellaneous / Newer Agents
- Ranolazine
- Trimetazidine
Mechanisms of Antianginal Drugs
Nitrates – Vasodilators
Mechanism: Release nitric oxide (NO) which relaxes vascular smooth muscle. This:
- Reduces preload (venous dilation)
- Reduces afterload (arterial dilation)
- Improves blood flow to coronary arteries
Overall, nitrates reduce oxygen demand and increase oxygen supply.
Beta Blockers
Mechanism: Reduce heart rate, blood pressure, and cardiac workload.
Uses: Stable angina (not helpful in variant angina).
Calcium Channel Blockers
Mechanism: Prevent calcium entry into smooth muscle cells, causing vasodilation and reduced heart workload.
Useful for:
- Stable angina
- Variant (spasm-related) angina
Nicotinate (Nicorandil)
Mechanism: Opens potassium channels and releases nitric oxide. This causes relaxation of both arteries and veins.
Ranolazine
Mechanism: Inhibits late sodium current in heart cells, reducing oxygen consumption.
Uses: Chronic stable angina.
Trimetazidine
Mechanism: Improves cardiac cell metabolism during low oxygen (cytoprotective).
Drug Profiles
Nitroglycerin
Form: Sublingual tablets, spray, patch, ointment.
Use: Immediate relief of acute angina attacks.
Side effects: Headache, flushing, low blood pressure.
Isosorbide Dinitrate
Long-acting nitrate used for angina prevention.
Atenolol / Metoprolol
Class: Beta-1 selective blockers.
Use: Stable angina and after heart attacks.
Verapamil / Diltiazem
Mechanism: Reduce heart rate and relax blood vessels.
Use: Variant angina and hypertension.
Amlodipine
Primarily vasodilator with minimal effect on heart rate.
Nicorandil
Dual action: Potassium channel opener + nitrate effect.
Ranolazine
Reduces oxygen consumption without altering heart rate or blood pressure.
General Adverse Effects
- Headache (common with nitrates)
- Dizziness
- Low blood pressure
- Flushing
- Slow heart rate (beta blockers, some CCBs)
- Ankle swelling (amlodipine)
Detailed Notes:
For PDF style full-color notes, open the complete study material below: