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Angina and Antianginal Drugs Drug classes and list: Amy J Davidoff '09 VASODILATORS (VENODILATORS) Nitrates: isosorbide dinitrate nitroglycerin Ca2+ channel blockers: dihydropyridines (DHPs): amlodipine, nifedipine diltiazem verapamil -ADRENERGIC RECEPTOR BLOCKERS: (without intrinsic sympathomimetic activity (ISA)) non-selective (1, 2): propranolol selective (1): metoprolol, atenolol Carvedilol (see HF drug list) - looks promising OTHERS: Anti-inflammatory drugs (ACE-I) Antiplatelet drugs (aspirin, clopidogrel) Lipid lowering drugs Late sodium channel blocker (e.g., ranolazine) If (sodium leak channel) blocker (ivabradine) Classification and pathophysiology of ischemic heart disease Brenner Fig 11-1 Angina myocardial O2 supply < ( coronary blood flow) O2 demand ( work) O2 extraction is near maximal even at rest O2 supply regulated by vascular resistance: Local factors (e.g., adenosine, bradykinin, prostaglandins, NO) Sherwood Fig 9-32 Coronary Blood Flow Guyton & Hall Fig 21-3 Dependent on: •Aortic diastolic pressure •Collateral blood flow •Arterial diameter (radius) •Epicardial-endocardial flow (subendo. arteries constrict more with ventricular contraction, particularly susceptible to ischemia) Figure 21-4 Phasic flow of blood through the coronary capillaries of left ventricle Normal Restricted circulation Martini Fig 20-10 The Hurst's The Heart, 8th ed Fill in desired therapeutic effects (and drugs classes) which would benefit an angina patient (with stable coronary artery disease (CAD)) Drug classes: Nitrates (NO) CCB BB Brenner Fig. 11-2 When oxygen supply does not meet demand ischemia LV dysfunction, pain, arrhythmias Strategies to treat angina Improve coronary blood flow and/or Decrease myocardial oxygen demand VASODILATORS Improve coronary perfusion - directly Decrease cardiac work – either on arterial side (red Afterload, or preload by venodilating dec venous return (reduce preload and/or afterload) BLOCKERS Decrease cardiac work (reduce HR and contractility) myocardial O2 supply coronaries Dilate arterioles systemic TPR Ca2+ channel blockers (high doses) cardiac work Nitrates Dilate veins (low doses) systemic preload Reflexes affecting heart TPR BP sympathetic activity blockers contractility HR work O2 demand Ca2+ channel blockers Do not combine verapamil and blockers (DHPs have little/no effects on heart muscle) NITRATES HEMODYNAMIC EFFECTS Venous vasodilatation Preload Pulmonary congestion Ventricular size Ventricular wall stress MVO2 Coronary vasodilatation Myocardial perfusion Arterial vasodilatation Afterload Shunting from ischemic area because already maximally dialyzed AHA website 2003 Nitroglycerin • Sublingual, oral, transdermal, buccal (IV preparations : Sodium nitroprusside (SNP), used in surgeries - potential risk of cyanide toxicity) • Onset and duration (dependent on route of administration) • Effective for treating or preventing effort (stable), variant and unstable angina • Side effects: reflex tachycardia, hypotension tolerance develops after 24 hours continuous use (prevented by 8-12h nitrate-free interval) Isosorbide dinitrate (mononitrate) •Sublingual, oral •Onset and duration (dependent on route of administration) (slower than nitroglycerin) •Tx or prevent angina •Reflex tachycardia, hypotension •Tolerance develops All the nitrates preferentially dilate large veins preload cardiac work and O2 demand Vasodilation via release of NO from endothelial cells Tolerance may be due to development of mitochondrial reactive oxygen species (ROS), which can inactivate nitrate reductase, resulting in inhibition of NO vasodilatory effects Proposed mechanism for preferential effects on venous side (compared to arterial side), regarding potency Preferential venodilation may be due to: •Duration of exposure diminishes response (tolerance) •Less endogenous NO in the veins (therefore veins more responsive than arteries) Kojda et al. Mol Pharm 53:547-554, 1998 Isosorbide mononitrate is the active metabolite Brenner Fig 11-4 Avoid using nitrates and Viagra Brenner Fig 11-3 Calcium Channel Blockers (Antagonists) • Inhibit inward calcium flux (through L-type channels) – Decrease myocardial and vascular smooth muscle contraction – Slow AV conduction and SA rate • Decrease afterload, contractility, heart rate, and improve myocardial blood flow • Agents differ in these activities • No adverse effects on lipid profiles (whereas B-blockers have adverse effects) Indications for Calcium Channel Blockers • Useful in stable and variant/vasospastic angina (not unstable angina) • Used to manage (prevent) angina (not treat attack) • Effort angina refractory to beta-blockers • Patients intolerant to beta-blockers and nitrates • Useful for 24 hour protection (vs nitrates) • “add on”, not monotherapy Ca2+ channel blockers Site of action dependent on tissue selectivity •Verapamil most cardiac selective (nodal cells and myocytes) •Diltiazem intermediate selectivity (SA node and vascular) •Dihydropyridines (DHPs) most vascular selective All have coronary vasodilatory effects (improve blood flow) DHPs Predominantly cause vasodilation: peripherally reduce TPR (~afterload) and cardiac work coronary vasodilation increase blood flow Amlodipine Long acting duration (days), T1/2 ~40hrs No effects on HR, nodal conduction, myocardial contractility Reflex tachycardia, arrhythmias Why? Nifedipine* Short acting duration (hours), T1/2 ~3hrs *ultra-short acting nifedipine may precipitate failure May depress myocardial contractility a little Reflex tachycardia, arrhythmias Verapamil and Diltiazem Duration (hours) Undergo significant first-pass hepatic metabolism Used for stable or variant angina (also used for certain arrhythmias) Usually contraindicated for ventricular dysfunction particularly verapamil (e.g., heart failure) Decreases cardiac work O2 demand Verapamil Slows A-V conduction and decreases myocardial contractility Diltiazem More selective for SA nodal cells than AV Toxicities are extensions of their therapeutic effects Choice of Tx in Chronic Stable Angina • ASA, lipid therapy (target LDL = <100mg/dL), ACEI • Short-acting NTG • Beta-blockers – Reduce mortality post-MI and in HTN • Calcium channel blockers (except rapid release nifedipine – b/c reflex tachycardia) – Rapid release forms may increase morbidity – May be preferred over long-acting nitrates (lack of tolerance) • Long-acting Nitrates – No effect on mortality with MI or CAD – Tolerance • Combination therapy before declaration of treatment failure Circulation 2003,107:149 Important Drug Interactions with Ca2+ Blockers • CYP 3A4 inhibitors (e.g., grapefruit juice) and amlodipine/felodipine – These DHPs are normally extensively metabolized • Amlodipine, verapamil, diltiazem and cyclosporin – Decreased cyclosporin metabolism with blockers • Verapamil and digoxin (cardiac glycoside) – Both slow A-V conduction (don’t combine them) • Verapamil and -blockers (don’t combine) – Too much cardiodepression -BLOCKERS IN ANGINA • Used to manage typical angina not effective for variant angina • Cardiac work (HR and SV) O2 demand • May improve O2 delivery by prolonging diastole (HR) • Long-term BP because of renin release (via 1 blocking) Other indications: • Use immediately after acute MI (improves survival) • Heart failure patients may benefit because of reduced myocardial ‘remodeling’ • Also used for certain arrhythmias, hypertension -Adrenergic Receptor Blockers Non-selective: 1-, 2-blocker propranolol pindolol (partial agonist (ISA)) rarely used ever, not indicated for angina Selective: 1-blocker metoprolol, atenolol 1-, 2- and 1- blockers: (discussed later) carvedilol, labetalol some indications for angina (not yet FDA approved) and HF • All -blockers are competitive inhibitors • Vary in lipophilicity, bioavailability, metabolism (i.e., pharmokinetics) • Some have unfavorable effects on lipids • Clinical problems with abrupt withdrawal because of receptor up-regulation - make more receptors/low concentration • Contraindications/precautions with Significant AV block, severe unstable LV failure, HR<50, SBP<90, asthma Less effective in blacks, use with caution in elderly (may CO too much), Asians may be more sensitive (may need to lower dose) more lipophilic Opie Fig 1-10, 1997 more hydrophilic Propranolol • Non-selective blocks both 1-AR and 2 –AR • Duration (hours) – same as metoprolol, shorter than atenolol • Low bioavailability because of 1st pass hepatic metabolism (highly lipid soluble) • MSA (membrane stabilizing activity) local anesthetic effects Side effects include: Slight TPR (sympathetic reflex), -AR intact • Bronchconstriction (via 2 blocking) • Renal blood flow (because CO) therefore, Na+, H2O retention (may need to add a diuretic) • May prevent response to hypoglycemia (via 2 blocking) and mask symptoms of hypoglycemia (e.g., tachycardia, sweating) care with diabetics (especially type 1) • May alter serum lipid levels ( VLDL and HDL) Side effects also include drowsiness. Why? Metoprolol & Atenolol • • • • Both selective 1-AR blockers = “cardioselective” Avoid bronchospasms Avoid masking hypoglycemia Both (-)renin (good effect), but may also renal blood flow via CO (like propranolol), therefore may need to add diuretic Metoprolol • Duration (hours) – similar to propranolol • Higher bioavailability and slightly less lipophilic than propranolol • Indicated for heart failure (MERIT-HF study) Atenolol • Much less lipophilic, therefore Less CNS effects (e.g., drowsiness) but may not have cardioprotective effects like metoprolol • Longer durations of action (longer half-live) Strategies for Combination Therapy Nitrates & -blockers nitrates reduce venous return (preload) -blockers prevent sympathetic reflex (decrease HR and cardiac work) DHPs & -blockers DHPs reduce TPR -blockers prevent sympathetic reflex Nitrates & DHPs (maybe diltiazem) nitrates reduce preload Ca2+ channel blockers reduce TPR (afterload) Nitrates, -blockers & DHPs nitrates reduce preload Ca2+ channel blockers reduce TPR -blockers prevent sympathetic reflex atherosclerosis diabetes (STEMI) (UA/NSTEMI) antiplatelet drugs (inhibit platelet aggregation) Antiplatelet and thrombolytic drugs covered in heme. From Golan et al. Principles of pharmacology: The pathophysiologic basis of drug therapy 2008 Note: In addition to aspirin: Clopidogrel or glycoprotein IIb-IIIa antagonists (antiplatelet agents) is recommended for acute coronary syndromes and subsequent to percutaneous coronary intervention New drug for stable angina: Ranolazine (ra noe' la zeen) used in combination with nitrate, BB or CCB (symptom prevention, not relief) mechanism in question (probably a late sodium channel blocker) Medical Letter June 2006; Circulation 2006; 113:2462-2472 Choice of Tx in Chronic Stable Angina • ASA, lipid therapy (target LDL = <100mg/dL), ACEI • Short-acting NTG • Beta-blockers – Reduce mortality post-MI and in HTN • Calcium channel blockers (except rapid release nifedipine) – Rapid release forms may increase morbidity – May be preferred over long-acting nitrates (lack of tolerance) • Long-acting Nitrates – No effect on mortality with MI or CAD – Tolerance • Combination therapy before declaration of treatment failure Circulation 2003,107:149 AHA/ACC Guidelines for Secondary Prevention for Patients with Coronary and Other Atherosclerotic Vascular Disease: 2006 Update Circulation 2006;113:2363-2372 and J Am Coll Cardiol 2006;47:2130-2139 Components of Secondary Prevention Cigarette smoking cessation Blood pressure control Lipid management to goal Physical activity Weight management to goal Diabetes management to goal Antiplatelet agents / anticoagulants Renin angiotensin aldosterone system blockers Beta blockers Influenza vaccination Guidelines are available on the Web sites of the AHA (www.americanheart.org) and the ACC (www.acc.org) Lipid-lowering Therapy (discussed later) • Goal = LDL <100mg/dL; perhaps as low as 70 • Diet/exercise • HMG CoA reductase inhibitors (statins): atorvastatin, lovastatin, pravastatin, simvastatin – Interfere with hepatic cholesterol production – Stabilize, lead to regression of coronary atherosclerotic plaques – Anti-inflammatory – Treating osteoporosis • 20-30% reduction in mortality and coronary events (Treatment Guidelines – Medical Records February 2008)