explain abtianginal drugs

Reading File

Finding Sources

Searching the Web

antianginal drugs mechanisms classification pharmacology

Finding Sources

Reading File

Finding Sources

Reading File

Finding Sources

I now have comprehensive content from authoritative sources. Let me compile the full answer.

Antianginal Drugs

Angina pectoris results from a mismatch between myocardial oxygen supply and demand. Antianginal drugs correct this by either reducing O₂ demand or increasing O₂ supply (or both). They fall into four major classes, plus newer second-line agents.

Pathophysiology Basis

Myocardial O₂ demand is determined by:

Heart rate (chronotropy)
Contractility (inotropy)
Wall stress = preload (ventricular filling pressure) + afterload (arterial resistance)

Any drug reducing one or more of these reduces angina in stable (exertional) angina. In vasospastic (Prinzmetal's) angina, the goal is to prevent or reverse coronary vasospasm.

Class 1: Organic Nitrates

Examples: Nitroglycerin (GTN), Isosorbide dinitrate (ISDN), Isosorbide mononitrate (ISMN)

Mechanism

Nitrates are bioconverted to nitric oxide (NO), which activates soluble guanylyl cyclase → ↑ cGMP → dephosphorylation of myosin light chains → smooth muscle relaxation and vasodilation.

Key hemodynamic effects:

Venodilation (primary) → ↓ preload → ↓ ventricular wall stress → ↓ O₂ demand
Arterial dilation (at higher doses) → ↓ afterload
Direct coronary vasodilation → relief of vasospasm; redistributes flow to ischemic subendocardium
In ACS: IV nitroglycerin rapidly titrated; contraindicated within 24 h of PDE5 inhibitor use (risk of profound hypotension)

Uses

Sublingual GTN: acute angina attack (onset 1–3 min)
Long-acting nitrates/patches: prophylaxis of stable angina
Vasospastic angina (first-line)

Tolerance

Continuous nitrate exposure causes nitrate tolerance (loss of efficacy). A daily nitrate-free interval of 8–12 hours is required (e.g., patch off at night).

Adverse Effects

Headache (most common — vasodilation of meningeal vessels), postural hypotension, reflex tachycardia, flushing.

Class 2: Beta-Blockers (β-Adrenoceptor Antagonists)

Examples: Metoprolol, Atenolol, Bisoprolol, Propranolol (non-selective), Carvedilol

Mechanism

Block β₁ receptors in the heart:

↓ Heart rate (chronotropy)
↓ Contractility (inotropy)
↓ AV conduction velocity

Net effect: ↓ myocardial O₂ consumption, especially during exercise. Also blunt sympathetic activation.

Uses

First-line for chronic stable angina (ACC/AHA and ESC guidelines recommend β-blockers as preferred initial therapy)
Post-MI (reduce mortality)
Preferred when angina coexists with hypertension, heart failure, or arrhythmias

Combination with nitrates

Beta-blockers block the reflex tachycardia triggered by nitrate-induced vasodilation. Nitrates counteract the ↑ end-diastolic volume (preload) caused by β-blockade. The combination is synergistic.

Adverse Effects

Bradycardia, fatigue, cold extremities, bronchoconstriction (non-selective), masking of hypoglycemia, sexual dysfunction. Contraindicated in vasospastic angina (β-blockade leaves α-adrenoceptors unopposed → may worsen vasospasm).

Class 3: Calcium Channel Blockers (CCBs)

Examples:

Dihydropyridines (DHPs): Nifedipine, Amlodipine, Felodipine — primarily vascular
Non-DHPs: Verapamil, Diltiazem — cardiac + vascular

Mechanism

Block voltage-gated L-type Ca²⁺ channels in cardiac and vascular smooth muscle. Drugs bind from the inner side of the membrane to open/inactivated channels → ↓ Ca²⁺ influx → smooth muscle relaxation.

Drug	Heart Rate	Contractility	Vasodilation
Verapamil	↓↓	↓↓	↑
Diltiazem	↓	↓	↑
Nifedipine/Amlodipine	↑ (reflex)	minimal	↑↑

Uses

Verapamil/Diltiazem: alternatives to β-blockers for chronic stable angina (especially if β-blockers contraindicated)
DHPs: preferred when heart rate is already low or β-blockers are not tolerated
Vasospastic angina: CCBs are first-line (both DHPs and non-DHPs)
DHPs + β-blocker combination: recommended for persistent angina

Adverse Effects

DHPs: peripheral edema, flushing, reflex tachycardia
Verapamil: constipation, bradycardia, heart block, negative inotropy (avoid in HFrEF)
Both: hypotension

Class 4: Second-Line (Newer) Agents

Ranolazine

Inhibits late inward Na⁺ current (late Iₙₐ) → reduces intracellular Na⁺ → reduces Ca²⁺ overload via Na⁺/Ca²⁺ exchanger → ↓ diastolic wall tension
No significant hemodynamic effects (does not lower BP or HR)
Can be combined with all other antianginal drugs
Used when angina is not controlled by first-line agents

Ivabradine

Selectively inhibits the If (funny) current (HCN channels) in the SA node → ↓ heart rate without affecting contractility
Used as an alternative to β-blockers in patients with normal sinus rhythm who cannot tolerate β-blockers
Caution: toxic when combined with β-blockers, verapamil, or diltiazem (additive bradycardia)

Nicorandil

Dual mechanism: K⁺-channel opener (arteriolar dilation, ↓ afterload) + nitrate-like effect (venodilation, ↓ preload)
Available outside the US; used as add-on therapy

Trimetazidine

Metabolic agent: inhibits fatty acid oxidation → shifts myocardial metabolism to glucose (more O₂-efficient)
No hemodynamic effects; used as add-on in Europe

Management Summary Table

(Adapted from ESC Guidelines, Goodman & Gilman's, 17th Ed.)

Situation	First-Line	Second-Line
Chronic stable angina	β-Blocker OR diltiazem/verapamil	Add DHP, long-acting nitrate, ranolazine, ivabradine
Vasospastic angina	CCB (DHP or non-DHP) + long-acting nitrate	Avoid β-blockers
Angina + low HR	Long-acting DHP	—
Angina + HF	Amlodipine (safe), avoid verapamil	Nicorandil, ranolazine
Acute attack	Sublingual GTN	IV nitroglycerin (ACS)
ACS	Aspirin + anticoagulant + β-blocker + nitrate	Reperfusion

Key Principles

All CAD patients should have short-acting sublingual nitrate as standby + aspirin + statin.
β-Blockers are preferred first-line for exertional stable angina due to evidence of fewer anginal episodes vs. nifedipine.
No significant outcome differences between long-acting nitrates, CCBs, and β-blockers overall, but β-blockers are guideline-preferred.
Combination therapy is additive: nitrate + β-blocker is the classic pair; DHP + β-blocker for refractory angina.
Ranolazine and trimetazidine act independently of hemodynamics and can be added to any regimen.

Sources: Katzung's Basic and Clinical Pharmacology, 16th Ed. | Goodman & Gilman's The Pharmacological Basis of Therapeutics, 13th Ed. | Fuster and Hurst's The Heart, 15th Ed.

also give me flashcards

Asking for Preferences

Reading File

Running Command

Writing File

Running Command

Your flashcard PDF is ready!

Antianginal Drugs Flashcards

PDF Document · PDF

The PDF contains 26 flashcards organized into 6 color-coded sections:

Color	Section
🔵 Blue	Basics of Angina (4 cards)
🟢 Green	Class 1 — Organic Nitrates (5 cards)
🟠 Orange	Class 2 — Beta-Blockers (5 cards)
🟣 Purple	Class 3 — Calcium Channel Blockers (5 cards)
🔴 Red	Class 4 — Second-Line Agents (4 cards)
🔵 Blue	Clinical Guidelines (3 cards)

Each card shows the question on top and the answer directly below — ideal for self-testing by covering the answer half. The source textbooks are credited in the footer.

This is a shared conversation. Sign in to Orris to start your own chat.