Classification of Antianginal Drug

Angina pectoris is a clinical syndrome characterized by chest pain or discomfort due to transient myocardial ischemia. It occurs when there is an imbalance between myocardial oxygen supply and demand. Antianginal drugs are used to relieve symptoms, improve exercise tolerance, and prevent future ischemic episodes.

This blog from Pharmacy Freak presents the classification, uses, drug of choice, adverse effects, and clinical updates on antianginal drugs as per standard pharmacological sources

What is Antianginal Drug

Antianginal drugs are medications used to prevent or relieve angina pectoris by improving the balance between oxygen supply and oxygen demand in the myocardium

Classification of Antianginal Drug (KD Tripathi)

Nitrates –
- Short acting: Glyceryl trinitrate, Isosorbide dinitrate (sublingual)
- Long acting: Isosorbide dinitrate (oral), Isosorbide mononitrate, Erythritol tetranitrate, Pentaerythritol tetranitrate
β–blockers: Propranolol, Metoprolol, Atenolol, others
Calcium channel blockers: Verapamil, Diltiazem, Amlodipine, Nitrendipine, others
Potassium channel opener: Nicorandil
Other antianginal drugs: Trimetazidine, Ranolazine, Ivabradine, Oxyfedrine, Dipyridamole

Classification of Antianginal Drug (General)

Antianginal drugs are classified into the following categories based on their mechanism of action:

Nitrates
Mechanism: Release nitric oxide → activate guanylate cyclase → increase cGMP → vasodilation
Effect: Dilate veins (↓ preload), arteries (↓ afterload), and coronary vessels (↑ supply)
Examples: Nitroglycerin, Isosorbide dinitrate, Isosorbide mononitrate
Use: Acute and chronic stable angina, variant angina
Beta-Adrenergic Blockers
Mechanism: Block β1 receptors → ↓ heart rate, ↓ contractility, ↓ blood pressure
Effect: Reduce myocardial oxygen demand
Examples: Metoprolol, Atenolol, Propranolol
Use: Chronic stable angina, post-MI angina
Note: Not useful in variant angina; may worsen vasospasm
Calcium Channel Blockers (CCBs)
Mechanism: Inhibit L-type calcium channels → reduce vascular tone and cardiac workload
Subtypes:
a. Dihydropyridines – Amlodipine, Nifedipine (mainly vasodilation)
b. Non-dihydropyridines – Verapamil, Diltiazem (vasodilation + cardiac depression)
Use: Stable and variant angina
Note: Diltiazem and Verapamil also control heart rate
Potassium Channel Openers
Mechanism: Activate ATP-sensitive K⁺ channels → arterial vasodilation
Example: Nicorandil
Use: Chronic stable angina
Note: Dual action (nitrate-like + K⁺ channel opening)
Metabolic Modulators
a. Ranolazine
Mechanism: Inhibits late inward Na⁺ current → ↓ intracellular Ca²⁺ → ↓ myocardial workload
Use: Chronic stable angina unresponsive to other drugs

b. Trimetazidine
Mechanism: Inhibits fatty acid oxidation → shifts metabolism to glucose oxidation (more efficient)
Use: Adjunct in chronic angina
Note: Improves myocardial energy efficiency

Sinus Node Inhibitors
Mechanism: Selective inhibition of If current → ↓ heart rate without ↓ contractility
Drug: Ivabradine
Use: Stable angina with high heart rate when β-blockers are not tolerated
Note: No effect on BP or myocardial contractility

Uses

Antianginal drugs are used in:

Stable angina (effort-induced)
Unstable angina (as part of acute coronary syndrome)
Variant (Prinzmetal’s) angina
Silent myocardial ischemia
Post-myocardial infarction prophylaxis
Prevention of exercise-induced ischemia
Pre-operative cardiac optimization

Drug of Choice Highlights

Stable angina – Nitroglycerin (acute), Beta blockers or CCBs (chronic)
Variant angina – Calcium channel blockers (especially Dihydropyridines)
Chronic angina unresponsive to other drugs – Ranolazine
Acute anginal attack – Sublingual Nitroglycerin
Angina with high heart rate – Ivabradine
Angina with hypertension – Beta blockers or Non-DHP CCBs
Post-MI angina – Beta blockers (especially cardioselective)
Angina in heart failure – Nitrates, Beta blockers, Ivabradine (if HR >70 bpm)

Side Effects

Nitrates – Headache, flushing, hypotension, tolerance (nitrate-free interval needed)
Beta blockers – Bradycardia, fatigue, bronchospasm, sexual dysfunction
CCBs – Ankle edema, hypotension (DHPs), bradycardia, AV block (Non-DHPs)
Ranolazine – Dizziness, constipation, QT prolongation
Ivabradine – Visual disturbances (phosphenes), bradycardia
Nicorandil – Headache, mouth ulcers
Trimetazidine – GI upset, extrapyramidal symptoms (rare)

Updated Clinical Pearls

Nitrates provide immediate relief in acute angina but tolerance develops on chronic use; a daily nitrate-free interval is essential.
Beta blockers reduce mortality after myocardial infarction and are a mainstay in chronic stable angina.
Non-dihydropyridine CCBs should be avoided with beta blockers due to risk of bradycardia and AV block.
Ranolazine is particularly useful in patients who cannot tolerate hemodynamic effects of traditional drugs.
Ivabradine selectively lowers heart rate without affecting blood pressure, making it suitable in normotensive patients with tachycardia.
Trimetazidine is used as an add-on therapy when conventional drugs are not fully effective.

References

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