Anti anginal drugs.
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Transcript of Anti anginal drugs.
ANTIANGINAL DRUGS
Presentation by- ANURAG CHANDAB.Pharm 6th semesterRoll no- 14Gurunanak institute of pharmaceutical science and technology.
Angina pectoris-
The primary cause of angina is an imbalance between myocardial oxygen demand and oxygen supplied by coronary vessels
This imbalance may be due to:
•a decrease in myocardial oxygen delivery•an increase in myocardial oxygen demand•or both
The discomfort abates when supply becomes adequate for demand. Typically angina lasts for seconds to minutes, up to 15 minutes
Classically angina is not associated with ischemic cell death
Types of Angina Pectoris
Stable Angina Variant Angina Unstable Angina
Effort , Typical. Atherosclerosis
Exercise, Emotion, Heavy meal. ↓ Pain
Prinzmetal. ↓ α- receptor mediated Vasoconstriction With or without atherosclerosis.
↓ Pain even at rest
Accelrated Severe typeDue to rupture of an atheromatous plaque attracting platelet deposition and progressive occlusion of the coronary artery
Antianginal AgentsThree major classes of agents are used
individually or in combination to treat angina:1. Organic nitrates:
Vasodilate coronary arteriesReduce preload and aferload
2. Beta-adrenergic blockers:Decrease heart rate and contractility - decrease
in cardiac work and O2 consumptionImprove myocardial perfusion due to decrease in
heart rate – decreased in ventricular wall tensionExercise tolerance
3. Calcium channel blockers:Vasodilate coronary arteriesReduce afterloadThe non-dihydropyridines (verapamil and
diltiazem) also decrease heart rate and contractility
Mechanism of Action of Nitrovasodilators
Nitric Oxide
activates
converts
Guanylate Cyclase*
GTPcGMP
activates
cGMP-dependent protein kinase
Activation of PKG results in phosphorylation of several proteins that reduce intracellular calcium
causing smooth muscle relaxation
Nitrates become denitrated by glutathione S-transferase
to release
Actions of Nitrates - GTN1. Preload reduction:
Dilatation of veins more than arteries – peripheral pooling of Blood – decrease venous return
Will lead to reduction in preload – decreased end diastolic size – decrease in fibre length
Less wall tension to develop for ejection (Laplace`s law) – less oxygen consumption and reduction in ventricular wall pressure (crunch abolished)
2. Afterload reduction: Some amount of arteriolar dilatation – Decrease in peripheral Resistance
(afterload reduction) – reduction in Cardiac work (also fall in BP) Standing posture – pooling of Blood in legs – reflex tachycardia
(prevented by lying down and foot end raising) However in large doses opposite happens – marked fall in BP – reflex
tachycardia – increased cardiac work – precipitation of angina
Actions of Nitrates - contd.
3.Mechanism of angina relief: Variant angina – coronary vasodilatation Classical angina – reduction in Cardiac load Increased exercise tolerance
4. Other actions: Cutaneous vasodilatation (flushing occurs), meningeal vessels dilatation (headache) and decreased renal blood flow
β-Adrenoceptor Blockers
β-Bs → Suppress the activation of the heart (β1). Reduce the work of the heart by ↓ heart rate& cardiac contractility → ↓ C.O.& slight ↓ B.P.
↓
Propranolol
.It is not a vasodilator , so it may worsen variant angina..
.It is used prophylactically to severity& frequency of typical anginal attacks.
.It cardiac O2 demand through: .-ve chronotropic & inotropic actions. .Slight of B.P.
Propranolol can be combined with Nitrates
for typical angina. ( to side effects of both drugs).
Ca++ channel blockers
Nifedipine, Verapamil, Diltiazem Mechanism of action on vascular tissue :
Blocking of Ca++ transmembrane channels in vascular smooth muscle fibers.
→ interference with inward of movement of Ca++
→ affects depolarization & contraction processes
→with relaxant effects mainly on arteriole smooth muscle.
Nifedipine: Prominent vasodilator actions, used in all types of angina with reflex tachycardia & leg œdema.
Verapamil: .Slows conduction & ↓ Heart rate. .Greater –ve inotropic effect with little Vasodialation effects. Diltiazem: .CVS effects similar to verapamil.
.It is used in angina by ↓ coronary spasm (variant angina).
Selection of antianginal drugs
For patients with concomitant diseases:
Concomitant disease Most preferred drugs
Less preferred drugs
Bronchial asthma.
Heart failure
Hypertension.
Diabetes Mellitus.
C.C.Bs, Nitrites& Nitrates.
Nitites & Nitrates.
β-Bs , C.C.Bs.
C.C,Bs ,Nitrites & Nitrates.
β-Bs.
β-Bs ,verapamil,Diltiazem.Nitrites & Nitrates.
β-Bs.
THANK
YOU
Reference-1) Tripathi K.D,Essentials of medical pharmacology. Sixth edition.2)Introduction to pharmacology by S.K kulkarni updated seventh edition.