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Anti-Anginal Drugs (Overview (Signs & Symptoms (typical angina…
Anti-Anginal Drugs
Overview
Angina pectoris
= sudden, severe, pressing chest radiating to the neck, jaw, back and arms
Atherosclerotic lesions
in coronary arteries can obstruct blood flow, leading to imbalance in myocardial oxygen supply & demand
Imbalance may also result during exertion & spasm of vascular smooth muscle
Transient episodes of myocardial ischemia
- occur from 15 secs to 15 mins - do not result in cellular death
Chronic ischemia
- lead to deterioration of cardiac function, heart failure, arrhythmia &
sudden death
Signs & Symptoms
typical angina pectoris- sudden, severe, crushing chest pain that may radiate to the neck, jaw, back & arms
dyspnea
atypical symptoms- indigestion, nausea, vomiting, diaphoresis
Nitrates
Mechanism of Actions
veins dilators, reduction in oxygen demand, effective for stable, rest angina, also dilate coronary vasculature causing increased blood supply to heart muscle
nitrates converted intracellularly to nitrite ions & to nitric oxide (NO) which activates guanylate cyclase, increases cGMP, leads to dephosphorylation of myosin light chain results in vascular smooth muscle relaxation
Examples
Nitroglycerin, Isosorbide dinitrate, Isosorbide mononitrate
Pharmacokinetics
onset of action varies from 1 minute (nitroglycerin) to 30 minutes (isosorbide mononitrate)
for prompt relief of angina attack caused by exercise or stress, sublingual (spray form) nitroglycerin is the choice, via sublingual to avoid hepatic first-pass effect
Adverse Effects
High doses- postural hypotension, facial flushing & tachycardia
Headache (most common)
contra-indicated with
Phosphodiesterase type 5 inhibitors
(sildenafil) because it potentiate action of nitrates
Tolerance
overcome by providing daily "nitrate-free interval", usually interval of 10-12 hrs at night
stable angina= 10 pm to 10 am (nitrate-free), 10 am to 10 pm (with nitrate patch),,,,, rest angina= 4 pm to 4 am (nitrate-free), 4 am to 4 pm (with nitrate patch)
B-blockers
Mechanism of Action
block B1 receptors resulting in decreased HR, contractility, CO & BP thereby decreasing oxygen demand
reduce frequency & severity of angina attacks, increase exercise duration & tolerance in patients with effort-induced angina
Examples
Atenolol, Bisoprolol,Metoprolol, Propanolol
Indications
recommended as initial anti-anginal therapy unless contra-indicated (eg: B-blockers are ineffective & may actually worsen symptoms of vasospastic angina)
for patients who had a prior MI, reduce mortality in patients with HPT & HFrEF
Adverse Effects
contra-indicated in patients with asthma, COPD, diabetes & severe bradycardia
dose gradually reduced over 2-3 weeks to avoid rebound angina, MI & HPT
Types of Angina
Rest (prinzmetal, variant, vasospastic)
may have significant coronary atherosclerosis but angina attack unrelated to physical activity, HR or BP
caused by decreased blood flow to heart muscle due to spasm of coronary artery
uncommon pattern, occurs at rest
respond promptly to coronary vasodilators (eg: nitroglycerin, CCBs)
Unstable
classified between stable angina & MI
chest pain occurs with increased frequency, duration & intensity (worsening)
not relieved by rest or nitroglycerin
considered as a form of
acute coronary syndrome
Stable (effort-induced, classic, typical)
may not present with any symptoms (silent angina)
short-lasting burning, heavy or squeezing feeling in chest
caused by reduction of coronary perfusion due to fixed obstruction of coronary artery produced by atherosclerosis
heart becomes vulnerable to ischemia whenever there is increased demand or other cause of increased cardiac workload (eg: physical activity, emotional stress or excitement)
most common, typical & stable
promptly relieved by rest or nitroglycerin
Therapeutic Management
Management of modifiable risk factors
hypertension
diabetes
dyslipidemia
Anti-anginal medications
B-blockers
CCBs (dihydropyridines, nondihydropyridines
Nitrates
Lifestyle modifications
physical activity
smoking cessation
weight management
CCBs
Mechanism of Actions
arteriolar vasodilators, inhibit entrance of calcium into cardiac & smooth muscle cells of coronary & systemic arterial beds
in treatment of effort-induced angina, decrease vascular resistance, decrease afterload, reduce myocardial oxygen demand
efficient in vasospastic angina (unlike B-blockers) due to ability to relax coronary arteries
Types
Dihydropyridines
arteriolar vasodilators, treat rest angina caused by spontaneous coronary spasm, minimal effect on cardiac conduction
Nondihydropyridines
affect calcium channel in heart, slows AV conduction directly & decreases HR, contractility, BP & thus the oxygen demand, greater negative inotropic effects, weaker vasodilator
contra-indicated in patients with pre-existing depressed cardiac function or atrioventricular conduction abnormalities, may cause gingival hyperplasia, can worsen HF
Verapamil (more towards heart), Diltiazem (can do both artery & heart)
Examples
Dihydropyridines (Nifedipine, Amlodipine, Felodipine), Nondihydropyridines (Verapamil, Diltiazem)