Block 2 Drug Summary

Question 1

What are ATII antagonists prescribed for? Mechanism of action? Example?

Answer 1

ATII Antagonists
- hypertension 
- antagonise RAAS 
- compete with ATII for binding to type 1 angiotensin receptor (AT1), resulting in 
o vasodilation 
o decreased TPR 
o suppression of aldosterone release 
- e.g. losartan

Question 2

What are ACE inhibitors prescribed for? Mechanism of action? Example?

Answer 2

ACE Inhibitors
- hypertension, congestive HF 
- inhibits ACE, preventing conversion of ATI to ATII, resulting in 
o decreased TPR 
o decreased aldosterone release 
- e.g. ramipril

Question 3

What are adrenal agonists prescribed for? Mechanism of action? Example?

Answer 3

Adrenal Agonists
- cardiac arrest, asthma 
- stimulates adrenoreceptors (α1, α2, β1, β2), triggering second messenger cascades 
o systemic vasoconstriction 
o increased heart contractility and HR 
o dilates bronchi 
o dilates cerebral vessels 
- e.g. adrenaline

Question 4

What are alpha blockers (antagonists) prescribed for? Mechanism of action? Example?

Answer 4

Alpha Blockers
- hypertension 
- inhibits α1 receptors, resulting in 
o vasodilation 
o decreased TPR 
- e.g. prazosin

Question 5

What are Class I antiarrhythmic drugs prescribed for? Mechanism of action? Example?

Answer 5

Class I: sodium channel blockers
o ventricular arrhythmia (incl. MI), anaesthesia (local, regional)
o stabilise potentially excitable membranes and prevent initiation and transmission of
nerve impulses
o e.g. lignocaine

Question 6

What are Class II antiarrhythmic drugs prescribed for? Mechanism of action? Example?

Answer 6

Class II: beta blockers 
o supraventricular arrhythmia, ventricular arrhythmia
o non-selective binding to β receptors reduces ability of noradrenaline to bind, 
resulting in 
 decreased HR 
 decreased force of contraction 
 decreased AV conduction 
o e.g. sotalol

Question 7

What are Class III antiarrhythmic drugs prescribed for? Mechanism of action? Example?

Answer 7

Class III: potassium channel blockers
o tachyarrhythmias not responding to other therapy (supraventricular, nodal,
ventricular, atrial flutter, AF, VF)
o prolongs AP duration and hence refractory period of atrial, nodal, ventricular tissue
o e.g. amiodarone

Question 8

What are Class IV antiarrhythmic drugs prescribed for? Mechanism of action? Example?

Answer 8

Class IV - Ca++ Channel Blockers
o supraventricular tachycardia, hypertension
o decreased influx of Ca2+, resulting in
 vasodilation
 slower AP propagation in SA and AV nodes
o e.g. verapamil

Question 9

What are antiplatelet drugs prescribed for? Mechanism of action? Example?

Answer 9

Antiplatelet Drugs
- mild to moderate pain, fever
- irreversibly inhibit COX-1, COX-2, resulting in decreased formation of prostaglandin
precursors and thromboxane and hence inhibited platelet aggregation and inflammatory
response
- e.g. aspirin

Question 10

What are non-aspirin antiplatelet drugs prescribed for? MoA? Example?

Answer 10

Non-aspirin antiplatelets
- prevention of ischaemic events in Px with symptomatic atherosclerosis
- selectively inhibit the binding of ADP to its platelet receptor, resulting in subsequent
inhibition of ADP mediated activation of GPIIb/IIIa complex, thereby inhibiting platelet
aggregation
- e.g. clopidogrel

Question 11

What are beta blockers (antagonists) prescribed for? Mechanism of action? Example?

Answer 11

Beta Blockers
- hypertension, angina pectoris, tachyarrhythmia, MI
- competitively block β receptors, resulting in
o decreased HR (neg. chronotropic)
o decreased contractility (neg inotropic)
o decreased SA and AV node conduction (neg. dromotropic)
- e.g. metoprolol

Question 12

What are beta agonists prescribed for? Mechanism of action? Example?

Answer 12

Beta Agonists
- Asthma, COPD
- Bind to beta receptors, stimulate adenylyl cyclase, increasing cAMP, activate PKA, activate MLC-P, Dephosphrylate myosin chains, decreasing myosin interaction and relaxing muscle.
E.g. - Salbutamol

Question 13

What are calcium channel blockers prescribed for? Mechanism of action? Example?

Answer 13

Ca Channel Blockers
- supraventricular tachycardia, hypertension
- decreased influx of Ca2+, resulting in
o vasodilation
o slower AP propagation in SA and AV nodes
- e.g. verapamil (antiarrhythmic)
- e.g. nifedipine (antihypertensive)

Question 14

What are cardiac glycosides prescribed for? Mechanism of action? Example?

Answer 14

Cardiac Glycosides
AF, congestive HF
- inhibits Na+/K+-ATPase, resulting in higher [Na+] inside cell, resulting in reduced Na+-
Ca2+ exchange, resulting in increased Ca2+ at SR, resulting in increased contractility
- e.g. digoxin

Question 15

What are cholesterol lowering drugs prescribed for? Mechanism of action? Example?

Answer 15

Cholesterol-lowering

• hypercholesterolaemia
• Antagonise HMG CoA reductase, leading to decreased synthesis of cholesterol in hepatocytes, upregulated LDL receptor synthesis
• e.g. pravastatin

Question 16

What are leukotriene antagonists prescribed for? Mechanism of action? Example?

Answer 16

Leukotriene antagonists
- asthma, allergic rhinitis
- inhibits cysteinyl leukotriene receptors on airway smooth muscle cells and airway
macrophages, resulting in
o decreased peripheral eosinophils
o decreased sputum eosinophils
o inhibited leukotriene induced bronchoconstriction from antigen challenge
 decreased inflammatory response in airways
- e.g. montelukast

Question 17

What are nitrates prescribed for? Mechanism of action? Example?

Answer 17

Nitrates
stable angina pectoris, HF associated with AMI
- GTN metabolised to NO, which activates GC, stimulating cGMP and secondary messenger
system resulting in smooth muscle relaxation and vasodilation
- e.g. glyceryl trinitrate (GTN)

Question 18

What are phosphodiesterase inhibitors prescribed for? Mechanism of action? Example?

Answer 18

Phosphodiesterase inhibitors.

• asthma, COPD
• MOA unclear: ? inhibits phosphodiesterase, resulting in increased cAMP  bronchodilation
• e.g. theophylline