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5 - Pharmacology > Anti-arrhythmic Drugs > Flashcards

Anti-arrhythmic Drugs Flashcards

1
Q

What are the different classifications for anti-arrythmic drugs?

A

1 = Na antagonists2 = B-blockers3 = K antagonists4 = Ca antagonists

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2
Q

Describe class 1

A

Voltage gated Na+ blockers- decrease conduction velocity- decrease automaticity- increase depolarisation threshold

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3
Q

Why are there different sub-classes of class 1 drugs?

A

Different effects on AP duration, effective refractory period and phase 0 slopeA = increase APD and ERP, moderate decrease in phase 0 slopeB = decrease APD and ERP, small reduction in phase 0 slopeC = no change in APD and ERP, large reduction in phase 0 slope

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4
Q

Give a 1a drug

A

quinidine

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5
Q

Give a 1b drug

A

Lidocaine

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6
Q

Give a 1c drug

A

Flecainide

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7
Q

Describe flecainide

A

Use for SVTsDon’t give in heart failure or with MI historyADRs = dizziness, vision disturbances and arrythmiasDDIs = CYP metabolism and renally excreted

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8
Q

Describe lidocaine

A

Use for ventricular arrhythmias after MIDon’t give in AV block or heart failureADRs = hypotension, bradycardia, nystagmus and seizures

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9
Q

Describe class 2

A

Beta-adrenoceptor blockers- block sympathetic action, decrease slope of pacemaker potential and decrease chronotropy- decreased automaticity- decrease phase 4 slope- increased threshold for activation in SAN and AVN- increase AVN conduction time and refractory period

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10
Q

When would you give a bete blockers?

A

Post MIAnginaHypertension Arrythmias

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11
Q

When would you not give a beta blocker?

A

AV blockHypotensionBradycardiaCongestive Heart Failure

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12
Q

ADRs of beta blockers

A

BronchospasmFatigue and insomniaCold extremitiesBradycardiaHypotensionDecrease glucose tolerance in diabetic patients

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13
Q

DDIs for beta blockers

A

Prevents salbutamol from working - antagonist overrides agonist actionsVerapamil - both are negative inotropes

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14
Q

Describe class 3 drugs

A

Block K+ channels- increases the absolute refractory period and the AP duration- suppresses re-entry circuits by closing excitable gap

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15
Q

Why are class 3 drugs not generally used?

A

Can be arrhythmic and increase the risk of torsades des points.

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16
Q

Give some examples of class 3 drugs

A

AmiodaroneSotalol - high dose (low dose gives a class 2 action)

17
Q

Why would you give class 3?

A

SVT and other ventricular arrythmias

18
Q

When would you not give a class 3 drug?

A

AV block

19
Q

DDIs of class 3 drugs

A

Amiodarone inhibits CYP enzymes and P-glycoprotein- need to reduce other drugs (warfarin, flecainide and digoxin)

20
Q

Describe class 4 drugs

A

Block Ca2+ channels- decrease slope of pacemaker AP at SAN and AVN- increases refractory period and decreases chronotropy and inotropy

21
Q

Examples of class 4 drugs

A

Verapamil Diltiazem

22
Q

When would you give class 4 drugs?

A

SVTProphylaxis for angina and hypertension

23
Q

When would you not give class 4 drugs?

A

Heart failureBradycardiaAVN block

24
Q

ADRS of class 4 drugs

A

HypotensionBradycardiaHeart failureHeart block

25
Q

Describe adenosine

A

AVN blocker- decrease automaticity- increases AVN refractory period- short t1/2- diagnoses and treats SVT

26
Q

Describe the mechanism for digoxin

A

Inhibits Na/K/ATPase which also inhibits Na/Ca exchanger. - increased intracellular Ca2+ causing an increase in inotropy Increases AVN refractory period and decreases conduction velocity of AVN

27
Q

ADRs of digoxin

A

Narrow therapeutic index, can easily lead to digoxin toxicity- cardiac toxicity (bradycardia, AVN block, atrial tachycardia)- toxicity is enhance with hypokalaemia

28
Q

What are the main ways to improve ventricular stroke volume and therefore the cardiac output?

A
  • Increase pre-load- Decrease after-load- Increase inotropy
29
Q

Why is increasing pre-load not a good option for someone in heart failure?

A
  • Heart is on flat region of frank-starling curve- Can exacerbate pulmonary and systemic congestion or oedema
30
Q

Describe how decreasing afterload helps to increase ventricular stoke volume

A

An increased afterload will reduced ejection velocity. Treating this will hale to increase stroke volume and decrease the pre-load which will help in improving the ejection-fraction.

31
Q

How does increasing inotropy help to improve ventricular stroke volume?

A

Increases stroke volume and ejection fraction. - Should only be used for acute systolic failure/ end stage failure as prolonged use can worsen outcomes and increase mortality. - Increase oxygen demand in the long term which is bad in the long term- Good acutely, as they increase stroke volume and ejection fraction but also decrease preload.

5 - Pharmacology (17 decks)

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