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Cardiology > Antiarrhythmic drugs > Flashcards

Antiarrhythmic drugs Flashcards

1
Q

Sources

A

https://wchh.onlinelibrary.wiley.com/doi/10.1002/psb.1828

https://bnf.nice.org.uk/drugs/amiodarone-hydrochloride/

https://go.drugbank.com/drugs/DB01118

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2
Q

What are the different classes of antiarrhythmic drugs?

A

Class I

Class II

Class III

Class IV

Class V

According to the Vaughan Williams classification

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3
Q

Which subgroup are Class I drugs further subdivided into?

A

Ia

Ib

Ic

Subdivided according to the speed at which they cause association/dissociation in non-nodal cardiac myocytes

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4
Q

Which type of antiarrhythmic drugs fall under class I?

A

Sodium channel blockers

Block Na+ influx

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5
Q

How fast do class Ia agents act?

A

Act at an intermediate speed

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6
Q

Give examples of class Ia agents

A

Quinidine

Procainamide

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7
Q

How fast do class Ib agents act?

A

Fastest acting

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8
Q

How fast do class Ic agents act?

A

Slow

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9
Q

Give examples of class Ib agents

A

Lidocaine

Mexiletine

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10
Q

Give an example of a class Ic agents

A

Flecainide

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11
Q

Which class I drugs are not commonly used in clinical practice?

A

Ia

They are anticholinergics

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12
Q

What can procainamide be used for?

A

Mx of ventricular and supraventricular tachyarrhythmias

Can be given PO, IM or IV

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13
Q

What type of reaction can procainamide commonly cause in some patients?

A

Lupus-like reaction

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14
Q

What can quinidine be used for?

A

Prevention of ventricular arrhythmias most notably in Brugada syndrome and idiopathic VF

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15
Q

What is lidocaine useful for apart from being a local anaesthetic agent?

A

Mx of VT when given IV

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15
Q

What are the adverse effects of quinidine?

A

Prolonged QT interval (can be useful in in managing short QT syndromes)

Nausea

Abdominal cramps

Increases digitalis toxicity

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16
Q

What are the adverse effects of IV lidocaine?

A

CNS excitation/depression

Cardiovascular instability (inc. arrhythmias and bradycardia)

Hypotension

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17
Q

What is the name of the drug that is an analogue of lidocaine but with oral bioavailability?

Is it licensed for use in the UK

A

Mexiletine

Not licensed for use in UK but can be imported on a case-by-case basis

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18
Q

What are class Ic drugs like flecainide used to manage?

A

Paroxysmal AF

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19
Q

What are important contraindications for class Ic drugs?

A

Previous MI

Sustained ventricular arrhythmias

Life threatening VT or shock can be induced in these settings

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20
Q

Which type of antiarrhythmic drugs fall under class II?

A

Beta blockers

They block catecholamines at beta1-adrenoceptors prolonging repolarisation

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21
Q

What are the indications for class II drugs?

A

Mx of tachyarrhythmias - Tx + prevention

Rate control in AF and atrial flutter

Can also be beneficial in chronic HF, after a MI and in glaucoma

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22
Q

Name the non-selective class II drugs

A

Propranolol (10-40 mg TDS-QDS)

Carvedilol (3.125-25mg BD - max 50 mg if < 85kg)

Labetalol (50-400mg BD)

Sotalol (40-160mg BD)

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23
Q

Name the cardioselective class II drugs

A

Bisoprolol (1.25-20 mg OD)

Atenolol (25-50 mg BD)

Metoprolol (50-100mg BD-TDS)

24
Q

Which type of antiarrhythmic drugs fall under class III?

A

Potassium channel blockers

25
Q

In the cardiac action potential, what are K+ channels responsible for?

A

Repolarisation

Essentially it allows the heart to become depolarised again

26
Q

What effect does blocking the K+ channels have on the action potential?

A

Slows repolarisation

Increases AP and refractory period

Slows conduction

Translate to a prolonged QT interval on ECG

27
Q

Give examples of class III drugs

A

Amiodarone

Sotalol (40-160mg BD)

Dronedarone

28
Q

What are the indications for amiodarone?

A

Rhythm control in AF/atrial flutter

Haemodynamically stable VF

29
Q

What are the adverse effects of amiodarone esp. after prolonged use (i.e., > 6 months)?

A

Arrhythmias

Hepatic disorders - abnormal liver enzymes

Hyperthyroidism

Pulmonary fibrosis

Photosensitivity

Skin reactions - blue-grey skin discolourations

Corneal microdeposits

Peripheral neuropathy

Does not improve mortality in patients with HF

30
Q

What are the rare side effects of amiodarone?

A

Bronchospasm in patients with respiratory failure

Headache

Idiopathic intercranial HTN

Nerve disorders

SIADH

31
Q

What are the contraindications for class III drugs?

A

Pre-existing prolonged QT interval - worsening of this may cause polymorphic VT

Bradycardia

AV block

32
Q

In which group of patients should sotalol be avoided?

A

HF

Significant renal impairment

Hypokalaemia

33
Q

Apart from the generic class III drugs side effect, what are the more specific side effects of sotalol?

A

Chest pain

Breathlessness

Palpitations

34
Q

Which type of antiarrhythmic drugs fall under class IV?

A

CCBs

Mainly the non-dihydropyridines

The dihydropyridines (e.g., amlodipine, nimodipine) do not have anti-arrhythmic properties

35
Q

Give examples of class IV drugs

A

Diltiazem (PO 60 mg TDS/60mg BD in elderly - max 360mg per day)

Verapamil (PO 40-120mg TDS OR slow IV infusion 5-10mg over 2 mins/over 3 mins in elderly)

36
Q

What are the indications of class IV drugs?

A

Prevention and Tx of SVTs:

  • rate control in AF/atrial flutter
  • fascicular VT

Helpful where beta-blockers are containdicated (e.g., in asthma) but should not be used concurrently with beta blockers due to risk of asystole

37
Q

What are the contraindications of class IV drugs?

A

HF - as they reduce cardiac contractility

38
Q

What are the adverse effects of class IV drugs?

A

Flushing

Dizziness

Headaches

Bradycardia

AV blocks

39
Q

What additional side effects can verapamil cause?

A

Constipation

Rash

Nausea

40
Q

What are class V agents?

A

Drugs that do not fit into the Vaughan Williams classification

41
Q

Give examples of class V agents

A

Digoxin

Adenosine

42
Q

What is the mechanism of digoxin?

A

Reduces HR via vagal effects

Mechanism not completely understood

43
Q

In which conditions is digoxin commonly used?

A

AF (rate control)

Atrial flutter

NOTE: it is not an anti-arrhythmic per se

44
Q

Which drugs can potentiate the effects of digoxin?

A

Quinidine

Amiodarone

CCBs

Beta blockers

45
Q

Which condition can potentiate the effect of digoxin?

A

Hypokalaemia

46
Q

What can digoxin toxicity cause?

A

Both brady- and tachyarrhythmias (atrial tachycardia and bidirectional VT)

47
Q

In which conditions is digoxin contraindicated?

A

AV block

Wolff-Parkinson-White syndrome

48
Q

When should digoxin be given with caution and its dose adjusted?

A

In the elderly

In renal impairment

49
Q

What is adenosine?

A

A purine nucleoside

Made from the breakdown of ATP

50
Q

What is the pharmacodynamics of adenosine?

A

binds Gi-protein type 1 receptors in cardiomyocytes

allows rapid K+ efflux and rapid hyperpolarisation and blocks Ca2+ influx

The reduces HR and conduction velocity by blocking AV node

51
Q

What is the half-life of adenosine?

A

10 seconds

(very short)

52
Q

How is adenosine commonly administered and used?

A

Commonly administered IV as a bolus in the management of SVT: either by cardioverting re-entrant tachycardias, or temporarily slowing the tachycardia to allow assessment of the underlying rhythm

53
Q

What can adenosine cause and what are the side effects associated with this?

A

Vasodilatation

  • headaches
  • flushing

Can also cause ‘feeling of impending doom’ as it cause bronchospasm

54
Q

What are the dosing of lidocaine when being used to treat arrhythmias

A

Ventricular arrhythmias, especially after myocardial infarction in patients without gross circulatory impairment
for lidocaine hydrochloride
Initially by intravenous injection
Adult
100 mg, to be given as a bolus dose over a few minutes, followed immediately by (by intravenous infusion) 4 mg/minute for 30 minutes, then (by intravenous infusion) 2 mg/minute for 2 hours, then (by intravenous infusion) 1 mg/minute, reduce concentration further if infusion continued beyond 24 hours (ECG monitoring and specialist advice for infusion), following intravenous injection lidocaine has a short duration of action (lasting for 15–20 minutes). If an intravenous infusion is not immediately available the initial intravenous injection of 100 mg can be repeated if necessary once or twice at intervals of not less than 10 minutes.

Ventricular arrhythmias, especially after myocardial infarction in lighter patients or those whose circulation is severely impaired
for lidocaine hydrochloride
Initially by intravenous injection
Adult
Initially 50 mg, to be given as a bolus dose over a few minutes, followed immediately by (by intravenous infusion) 4 mg/minute for 30 minutes, then (by intravenous infusion) 2 mg/minute for 2 hours, then (by intravenous infusion) 1 mg/minute, reduce concentration further if infusion continued beyond 24 hours (ECG monitoring and specialist advice for infusion), following intravenous injection lidocaine has a short duration of action (lasting for 15–20 minutes). If an intravenous infusion is not immediately available the initial intravenous injection of 50 mg can be repeated if necessary once or twice at intervals of not less than 10 minutes.

55
Q

What are the dosing of amiodarone?

A

Treatment of arrhythmias, particularly when other drugs are ineffective or contra-indicated
PO
200 mg 3 times a day for 1 week, then reduced to 200 mg twice daily for a further week, followed by maintenance dose, usually 200 mg daily or the minimum dose required to control arrhythmia

IV
Initially 5 mg/kg, to be given over 20–120 minutes with ECG monitoring, subsequent infusions given if necessary according to response; maximum 1.2 g per day.

Ventricular fibrillation or pulseless ventricular tachycardia refractory to defibrillation (for cardiopulmonary resuscitation)
IV
Initially 300 mg, dose to be given over at least 3 minutes, dose should be given from a pre-filled syringe or diluted in 20 mL Glucose 5%, then 150 mg if required, consult Resuscitation Council (UK) guidelines for further details.

56
Q

What is the dosing of digoxin?

A

Rapid digitalisation, for atrial fibrillation or flutter
0.75–1.5 mg in divided doses, dose to be given over 24 hours, reduce dose in the elderly.

Maintenance, for atrial fibrillation or flutter
Maintenance 125–250 micrograms daily, dose according to renal function and initial loading dose, reduce dose in the elderly.

Heart failure (for patients in sinus rhythm)
62.5–125 micrograms once daily, reduce dose in the elderly

Emergency loading dose, for atrial fibrillation or flutter
Loading dose 0.75–1 mg, to be given over at least 2 hours, then (by mouth) maintenance - reduce dose in elderly

57
Q

What is the dosing of adenosine?

A

Rapid reversion to sinus rhythm of paroxysmal supraventricular tachycardias, including those associated with accessory conducting pathways (e.g. Wolff-Parkinson-White syndrome),
Used to aid to diagnosis of broad or narrow complex supraventricular tachycardias

Initially 6 mg, administer into central or large peripheral vein and give over 2 seconds, cardiac monitoring required, followed by 12 mg after 1–2 minutes if required, then 12 mg after 1–2 minutes if required, increments should not be given if high level AV block develops at any particular dose

Rapid reversion to sinus rhythm of paroxysmal supraventricular tachycardias, including those associated with accessory conducting pathways (e.g. Wolff-Parkinson-White syndrome) in patients with a heart transplant,
Aid to diagnosis of broad or narrow complex supraventricular tachycardias in patients with a heart transplant
Initially 3 mg, administer into a central or large peripheral vein and give over 2 seconds, followed by 6 mg after 1–2 minutes if required, then 12 mg after 1–2 minutes if required, patients with a heart transplant are very sensitive to the effects of adenosine.

All are RAPID IV INFUSIONS

58
Q

What is adenosine used to treat?

A

Supraventricular tachycardia (SVT)

Cardiology (15 decks)

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