Pharmacotherapy of Angina Pectoris
Definition
Types of angina
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▪ Angina pectoris refers to a strangling or pressure-like pain caused by cardiac ischemia.
▪ The pain is usually located sub sternally but is sometimes perceived in the neck, shoulder and arm, or
epigastrium.
▪ Drugs used in angina exploit two main strategies: reduction of oxygen demand and increase of oxygen
delivery to the myocardium.
Angina pectoris
Pathophysiology
Management
Organic Nitrates
▪ Organic nitrates are prodrugs – they release nitric oxide (NO).
▪ Nitrates are mainly venodilators, also cause arteriolar dilatation, thus reduce both preload and afterload.
Pharmacological actions:
On vascular/GI/respiratory smooth
muscle: relaxation.
Nitroglycerin quickly relieves anginal pain
by decreasing the O2 requirement and
increasing O2 delivery to the myocardium.
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Mechanism of Action- Nitrates
Nitrates decrease coronary vasoconstriction or spasm
and increase perfusion of the myocardium by relaxing
coronary arteries.
Organic nitrates
activates guanylate cyclase
increases cGMP
Elevated cGMP ultimately leads to dephosphorylation of the myosin light chain, resulting in
vascular smooth muscle relaxation.
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Convert into nitrite ions then into nitric
oxide
Organic Nitrates
Pharmacokinetics:
Adverse Effects:
▪ Absorbed through buccal mucosa, skin, and GI tract.
▪ Low oral bioavailability due to first-pass metabolism
(except isosorbide mononitrate).
▪ Sublingual route: Rapid onset (2–5 min), short
duration.
▪ Transdermal route: Slow absorption, prolonged effect.
▪ Excretion: Metabolites in urine as glucuronide
derivatives.
▪ Due to vasodilation: Headache, postural
hypotension, tachycardia, palpitation, flushing,
weakness, and rarely syncope.
▪ Overdose: Methaemoglobinaemia.
Tolerance:
▪ Develops with prolonged use (oral, transdermal, IV).
▪ Rare with intermittent use (e.g., sublingual GTN).
▪ Mechanisms: Reduced NO generation, sulphydryl depletion, free radical formation.
▪ Cross-tolerance occurs.
▪ Prevented by a nitrate-free interval (8–12 hours daily).
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▪ To reduce symptoms, spit out sublingual tablet
once pain is relieved.
Therapeutic uses of Nitrates
Isosorbide Dinitrate:
Isosorbide Mononitrate:
▪ Sublingual for acute anginal attacks.
▪ Oral for chronic prophylaxis (low bioavailability
due to first-pass metabolism).
▪ Preferred for chronic angina prophylaxis.
▪ Longer duration of action.
▪ High oral bioavailability (no first-pass
metabolism).
Treatment of Cyanide Poisoning
β Adrenergic Blockers
The beneficial effects of β-blockers in exertional angina are mainly due to negative chronotropic and
negative inotropic effects.
▪ Cardioselective β -blockers are preferred.
▪ β -Blockers with intrinsic sympathomimetic activity (e.g. pindolol) should be avoided as they may worsen
angina.
Reasons for Using Nitrates with Beta-Blockers in Angina
▪ Nitrates provide rapid vasodilation, relieving angina but may cause reflex tachycardia.
▪ β-Blockers prevent tachycardia, reduce myocardial workload, and improve oxygen efficiency.
▪
They are, however, contraindicated in patients with asthma, diabetes, severe bradycardia,
peripheral vascular disease, or chronic obstructive pulmonary disease.
▪
Note: It is important not to discontinue β- blocker therapy abruptly. The dose should be gradually
tapered off over 5 to 10 days to avoid rebound angina or hypertension.
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▪ The combination is superior in chronic angina management by balancing oxygen demand and supply
while minimizing side effects.
Calcium Channel Blockers
1. Phenylalkylamine: Verapamil.
2. Benzothiazepine: Diltiazem.
3. Dihydropyridines (DHPs): Nifedipine, amlodipine, cilnidipine, nicardipine, felo dipine, isradipine, nisoldipine,
lacidipine.
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Pharmacological actions
Mechanism of Action.
▪ Voltage-sensitive Ca2 channels are of five subtypes:
-L, N, T, P and R.
▪ L-type is predominantly present in cardiac and smooth
muscle cells.
Therapeutic uses-CCBs
Potassium Channel Openers (Potassium Channel Activator)
Nicorandil is administered orally.
▪ It causes arteriolar and venodilation, and also improves coronary blood flow.
▪ Tolerance does not develop to its actions.
▪ The side effects are head ache, hypotension, palpitation, flushing, nausea, vomiting,
ulcers in the mouth, etc.
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Drug summary- Antianginal drugs