Cardiac Drugs

Question 1

Aspirin

Answer 1

• Aspirin prevents formation of PGs which both inhibits (blocks thromboxane A2) and promotes aggregation (blocks prostacycline)
• Thromboxane is reduced for lifespan of the platelet
• Prostacycline inhibition is reversible
• Twice weekly, 100-600mg, enteric coating

Question 2

Purinergic antagonists

Answer 2

• Antiplatelets
• ADP induced platelet aggregation by activating P2Y12 receptors
• Activation –> decreased cAMP –> increased platelet aggregation
• Eg. Clopidogrel

Question 3

Clopidogrel

Answer 3

• Anti-platelet via P2Y12 receptor
• Prodrug
• Converted by CYP enzymes
• Prevention of ischaemic events with symptomatic atherosclerosis

Question 4

GP IIb/IIIa inhibitors

Answer 4

• Prevent fibrinogen cross-linking of platelets
• Abiciximab
• Tirofiban

Question 5

Direct thrombin inhibitors

Answer 5

• Do not rely on endogenous anticoagulant systems
• Dabigatran
• Prevention of venous thromboembolism and non-valvular AF
• Gastric effects

Question 6

Rivaroxaban

Answer 6

• inhibits factor Xa
• similar usage to Dabigatran

Question 7

Heparins

Answer 7

• Not absorbed by gut –> IV or subcutaneous
• Enhances anti-thrombin –> inactivation of Xa and thrombin
• Prevention of venous thrombus, treatment of venous thromboembolism, peripheral arterial occlusion, acute coronary syndrome
• Main risk haemorrhage

Question 8

Vitamin K antagonists

Answer 8

• Vit K required for synthesis of factors II, VII, IX, X
• Warfarin

Question 9

Warfarin

Answer 9

• Competes with Vit K for binding at VKORC1
• Metabolised by CYP2C9
• Peak pharm effect 48h
• Requires monitoring
• P450 interaction
• Crosses placenta

Question 10

Fibrinolytics

Answer 10

• Cleave plasminogen to plasmin
• Plasmin digests fibrin, fibrinogen, ECM proteins, clotting factors
• Dissolve clots and reopen occluded arteries
• Patient with acute MI <12h
• Alteplase
  
  • IV
  • Major risk of bleeding

Question 11

Class I Anti-arrhythmics

Answer 11

• Block Na channels
• Bind to a subunit to prevent Na entry
• Slow conduction velocity of pacemaker potentials
• Used for tachyarrhythmias

Question 12

Class 1a antiarrhythmics

Answer 12

• Disopyramide –> life-threatening tachycardias
• Quinidine
• Slows phase 0 of CAP
• Increases refractory period

Question 13

Class 1b antiarrhythmics

Answer 13

• Fast <0.5s
• Limited effects on conduction velocity
• Lignocaine –> serious ventricular arrhythmias
• More activity with increased HR

Question 14

Class 1c anti-arrhythmics

Answer 14

• Slow
• Flecainide
• Slows cardiac conduction esp in ventricles
• Prolongs PR and QRS intervals
• AF, atrial flutter, SVT
• CI: heart block, MI

Question 15

Class 2 antiarrhythmics

Answer 15

• Anti-sympathetic effect at SA and AV nodes
• Atenolol
• Metoprolol
• Tachycardias
• Also neg inotrope –> reduced Ca influx

Question 16

Ivabradine

Answer 16

• Angina
• Chronic heart failure
• Inhibits If
• Negative chonotrope

Question 17

Class 3 antiarrhythmics

Answer 17

• Prolong cardiac action potential
• Block K outward channels
• Increases refractory period
• Prevents re-entrant tachycardia
• Supresses ectopic activity
• Eg. Amiodarone

Question 18

Amiodarone

Answer 18

• Class 3
• Reduces automaticity
• Prolongs PR and QT intervals
• Prolongs refractory periods
• Serious tachycardias
• Inhibits CYP2C9, CYP2D6 àmultiple drug interactions
• Very long elimination half life (10-100 days)

Question 19

Sotalol

Answer 19

• Dual class II/III
• Blocks b adrenoreceptors and K channel
• Treatment and prevention of atrial, SV and ventricular arrhythmias

Question 20

Class 4 antiarrhythmics

Answer 20

• Ca channel antagonists
• Slow the conduction of SA and AV nodes
• Reduce contractile force
• Verapamil, Diltiazem

Question 21

Verapamil

Answer 21

• Class 4
• Greater cardiac effects
• SVT, AF, atrial flutter

Question 22

Diltiazem

Answer 22

• Class 4
• Acts on cardiac and vascular smooth muscle
• Less cardiac effects than verapamil

Question 23

Atropine

Answer 23

• Competitive antagonist of muscarinic receptors
• Treatment of bradycardia and haemodynamic compromise
• Removes parasympathetic brake on HR
• Reverse SLUDGE BBB effects

Question 24

Isoprenaline

Answer 24

• B agonist
• Positive inotrope, positive chonotrope
• Heart block
• Bradycardia with haemodynamic compromise

Question 25

Digoxin

Answer 25

• Increases ventricular output
• Positive inotrope
• HF and some arrhythmias
• Long elimination time
• Narrow TR