Comprehensive Overview of Antianginal Drugs

 

Antianginal Drugs: Comprehensive Overview 

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 Types of Angina

1. Stable Angina (Effort Angina): Occurs with exertion or stress.
2. Unstable Angina: New, worsening, or rest angina; precursor to myocardial infarction.
3. Prinzmetal’s Angina (Variant Angina): Coronary artery spasm, often at rest.

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Classification of Antianginal Drugs

1. Nitrates (e.g., Nitroglycerine, Isosorbide dinitrate, Isosorbide mononitrate)
2. β-Blockers (e.g., Propranolol, Metoprolol, Atenolol)
3. Calcium Channel Blockers (e.g., Verapamil, Diltiazem, Nifedipine, Amlodipine)
4. Potassium Channel Openers (e.g., Nicorandil)
5. Miscellaneous (e.g., Ranolazine)

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Mechanism of Action of Nitrates

• Nitrates release nitric oxide (NO) in vascular smooth muscle.
• NO activates guanylate cyclase, increasing cyclic GMP.
• Results: Smooth muscle relaxation, venodilation, and reduced preload and afterload.

Visual: Simplified flowchart of nitrate action from NO release to vasodilation.

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Nitrates: Clinical Aspects

• Indications: Stable angina, acute coronary syndrome, CHF.
• Adverse Effects: Headache, hypotension, reflex tachycardia.
• Contraindications: Hypotension, concurrent PDE-5 inhibitors (e.g., sildenafil).
• Drug Interactions: PDE-5 inhibitors potentiate hypotensive effect.

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Mechanism of Action of β-Blockers

• Block β1 adrenergic receptors, reducing heart rate and contractility.
• Decrease myocardial oxygen demand.
• Anti-arrhythmic properties.

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β-Blockers: Clinical Aspects

• Indications: Stable angina, post-MI, hypertension.
• Adverse Effects: Bradycardia, fatigue, bronchospasm (non-selective).
• Contraindications: Asthma (non-selective), severe bradycardia.
• Drug Interactions: Additive effects with other cardiac depressants (e.g., digoxin).

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Mechanism of Action of Calcium Channel Blockers (CCBs)

• Inhibit L-type calcium channels in smooth muscle and myocardium.
• Result: Vasodilation, reduced contractility, and decreased myocardial oxygen demand.

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Calcium Channel Blockers: Clinical Aspects

• Indications: Stable angina, Prinzmetal’s angina, hypertension.
• Adverse Effects:
• Dihydropyridines (e.g., amlodipine): Peripheral edema, reflex tachycardia.
• Non-dihydropyridines (e.g., verapamil): Bradycardia, constipation.
• Contraindications: Severe bradycardia (verapamil, diltiazem).
• Drug Interactions: Caution with β-blockers (risk of AV block).

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Mechanism of Action of Potassium Channel Openers (Nicorandil)

• Activates ATP-sensitive potassium channels.
• Causes hyperpolarization and vascular smooth muscle relaxation.
• Has nitrate-like NO-donating properties.

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Nicorandil: Clinical Aspects

• Indications: Stable and Prinzmetal’s angina.
• Adverse Effects: Headache, flushing, gastrointestinal ulceration (rare).
• Contraindications: Severe hypotension.
• Drug Interactions: Additive hypotension with nitrates or antihypertensives.

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Rationale of Combination Therapy

• Combination therapy improves angina control and minimizes side effects:
• Nitrates + β-blockers: Prevent reflex tachycardia from nitrates.
• CCBs + β-blockers: Balanced HR and afterload control.
• Nicorandil + β-blockers: Enhanced oxygen supply and demand balance.

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Presentation for Antianginal Drugs

   

                                                END OF THE CHAPTER

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