Anti anginal drugs naser
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Drugs used for ischemic heart disease, angina for MBBS, dental students of pharmacology
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Anti anginal drugs naser
- 2. Angina pectoris • Main symptom of IHD • Occurs due to imbalance between oxygen supply and oxygen demand of myocardium • Clinical types – Stable angina – Prinzmetals angina – Unstable angina
- 3. Pathophysiology ↓ O2 supply ↑ O2 demand Coronary • Atherosclerosis • Vasospasm • Thrombosis • ↑↑ HR • Ventricular Hypertrophy ↑↑Contractility ↑↑Wall tension
- 4. Treatment ↑ O2 supply ↓ O2 demand • PTCA/CABG • Relieve vasospasm • CCB, Nitrates •Break thrombi •Thromolytics •Prevent thrombi • Antiplatelets By ↓ work load on heart •Preload : Nitrates •After load: CCB, K+ channel openers •HR & contractility: - Blockers
- 5. Classification of drugs • For treatment of acute anginal attack – Nitroglycerine, isosorbide dinitrate (SL) • For Chronic prophylaxis – Nitrates: • Nitroglycerine, Isosorbide di nitrate, isosorbide mononitrate, penta erythritol tetranitrate – Beta blockers – Calcium channel blockers • Verapamil, diltiazem, Amlodipine – Potassium channel opener • Nicorandil, Pinacidil – Miscellaneous • Dipyridamole
- 6. Nitrates (Mechanism of Action) Nitrates Denitrated in smooth muscle cell Release NO + Guanyl Cyclase ↑ cGMP Dephosphorylation of MLC Relaxation of vascular smooth muscles Mainly Venodilation Arterial dilation Dilation of coronary vessels
- 7. Pharmacological actions Venodilatation Pooling of blood ↓↓Venous return ↓↓ preload ↓↓ cardiac work ↓↓ O2 requirement Arterial dilatation ↓↓PVR ↓↓ Afterload Relief of anginal pain Dilatation of large coronary vessels & collaterals ↑↑ Blood flow to ischemic area ↑↑ oxygen delivery to ischemic area
- 8. Pharmacokinetics • Absorbed through buccal mucosa, skin & GIT • All except Isosorbide Mononitrate undergo extensive first pass metabolism • SL route produces rapid onset 2-5 Min, but shorter DOA • Absorption through skin is slow
- 9. Adverse effects • Headache • Postural hypotension • Tachycardia, palpitations • Weakness • Flushing • Tolerance on prolonged use • Overdosage may cause methemoglobinemia
- 10. Uses of Nitrates • Angina: – Sublingual NTG drug of choice for acute anginal attacks – Oral nitrates can be used for prophylaxis of angina • Myocardial Infarction • Congestive heart failure • Biliary colic • Cyanide poisoning • Esophageal spasm
- 11. -blockers • Reduce frequency and severity of anginal attacks of exertional angina • Used for long term prophylaxis of classical angina , may be combined with nitrates • MOA: – ↓ oxygen consumption by ↓contractility & HR • Selective Beta blockers are preferred
- 12. Calcium channel blockers Block Voltage sensitive L-type of Ca2+ channels Prevent entry of calcium into the cell No excitation contraction coupling in the heart and vascular smooth muscles Myocardial contractility Cardiac work & oxygen consumption Coronary vasodilation Relaxation of Vascular smooth muscles ↓ PVR & After Load
- 13. Calcium channel blockers • Verapamil : Predominant action on heart – ↓ force of contraction & heart rate – Causes bradycardia so not given with -blockers – Less potent vasodilator • Nifedipine: – Potent vasodilator causes significant fall in BP – Evokes reflex tachycardia – Weak myocardial depressant – Can be given sublingually
- 14. Other calcium channel blockers • Amlodipine • Nimodipine • Diltiazem • Nitrendipine
- 15. Pharmacokinetics • All CCBs well aabsorbed through GIT • Undergo varying degree of first pass metabolism • Highly bound to plasma proteins
- 16. Adverse effects • Headache, Flushing • Reflex tachycardia, Palpitations • Postural hypotension • Ankle edema • Leg cramps • Dizziness • Verapamil can cause constipation , sinus bradycardia, AV block
- 17. Uses • Angina pectoris • Hypertension • Paroxysmal Supraventricular tachycardia • Peripheral vascular disease • Migraine: verapamil
- 18. Potassium channel openers (Nicorandil) Open ATP dependent potassium channels Potassium efflux Hyperpolarization of membrane Venodilatation Arterial Dilatation Decrease after load Decrease preload
- 19. Pharmacotherapy of angina • Acute anginal attack: – Tab Nitroglycerine 0.5 mg sublingually, if pain is not relieved within 5 min, repeat dose but not more than 3 tablets in 15 min • Prophylaxis (Prevention of further attacks) – Long acting nitrates , Beta blockers, calcium channel blockers
- 20. Treatment of Myocardial infarction • Inj morphine sulphate 10 mg IV • Oxygen • Antiemetic: promethazine • Aspirin 75 -150 mg, clopidogrel 75 mg OD • Fibrinolytics: streptokinase, alteplase • Anticoagulants • Beta blockers • ACE inhibitors • Statins
- 21. Combination of drugs in angina • Nitrates + -blocker – Reflex tachycardia by nitrates ↓ by -blockers • Nifedipine + -blocker – Reflex tachycardia countered by -blockers • Nitrates + calcium channel blockers – Nitrates ↓ preload, CCBs ↓ afterload • CCB + -Blocker + Nitrates – If not controlled by 2 drugs
Editor's Notes
- Angere = to strangulate, pectolaris = chest
- Trimetazidine, oxyfedrine
- Prodrugs , release nitric oxide , only major action is non specific smooth muscle relaxation Venodialtion reuces the preload, arterial dilation reduces the vascular resistance thus after load , as both preload and after load are decreased work load of heart is decreased thereby reducing the oxygen requirement, in variant angina nitrates relieve vasospasm due to coronary vasodilation.
- Vascular smooth muscles 2. Other smooth muscles?: smooth muscles of bronchii, esophagus, biliary tract etc are relaxed by nitrates.
- Absorption through skin is slow: therefore this route is used for prolonged effect and sublingual route is preferred in emergency. Metabolites are excreted mainly in urine as glucuronide derivatives
- These adverse events are because of extensive vasodilation. To avoid these symptoms the tablet may be spit out as soon as pain is relieved.
- Read from KDT & prep manual
- Do not dilate coronary arteries or other blood vessels , total coronary blood flow is rather reduced due to blockaade of dilator Beta 2 receptors . However flow to ischemic subendocardial area is not reduced due to favourable redistribution and decrease in ventricular wall tension. They act by reducing the cardiac work and oxygen consumption . This is marginal at rest. More importantly they limit increase in these modalities that occur during exercise or anxiety, due to antiadrenergic action, all beta blockers are equally effective in decreasing frequency and severity of attacks and in increasing the exercise tolerance in classical angin, but cardioselective agents are preferred over non selective which may worsen the angina due to unapposed alpha receptor mediated coronary constriction, that may accenuate the coronary spasm. Long term beta blocker therapy lowers risk of sudden cardiac deathamong IHD They should be taken on regular basis and not as when required , abrupt discontinuation after chronic usage may precipitate severe attack even MI. Unstable angina: (NSTEMI) Should be used only after starting nitrate±calcium channel blocker to counteract coronary spasm. If present Beta blockers carry risk of worsening coronary vasospasm. Beta blockers reduce myocardial oxygen demand and afford additional benefit by reducing risk of impending MI / sudden cardiac death.
- Voltage sensitive calcium channels are of five types LPRNT, L type is predominantly present in cardiac & smooth muscle cells
- Other calcium channel blockers like amlodipine, felodipine , nitrendipine, nicardipine are similar to nifedipine but with some pharmacokinetic variations Nimodipine has selectivtiy for cerebrovascular vessels
- Diltiazem is potent vasodilator but also a potent myocardial depressant
- Metabolized in liver excreted in urine
- Adverse effects: headache, flushing, dizziness They are administered orally, their efficacy is similar to nitrates, beta bolckers or CCBs . The main advantage of nicorandil is that it has a longer duration of action and does not cause tolerance