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10 Minutes of Study Time > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

What are the classes of anti-arrhythmics?

What is the mechanism of each one?

A 
Class I - Sodium channel blockers
Class II - Beta blockers
Class III - Potassium channel blockers
Class IV - Calcium channel blockers
Other - Atropine and Digoxin

Class I is split into a, b and c dependent on their effects on the refractory period.
Class Ia increases the refractory period
Class Ib decreases the refractory period
Class Ic has no effect on the refractory period, depresses phase 0.

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2
Q

What are some examples of Class Ia anti-arrhythmics?

What is the mechanism?

A

Quinidine
Dixopyramide

Sodium channel blockers, increasing the refractory period.

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3
Q

What are some examples of Class Ib anti-arrhythmics?

What is the mechanism?

A

Lignocaine
Phenytoin

Sodium channel blockers, decreasing the refractory period

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4
Q

What are some examples of Class Ic anti-arrhythmics?

What is the mechanism?

A

Flecainide
Encainide
Propafenone

Sodium channel blockers, depress phase 0 without having an effect on refractory period

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5
Q

What class of antiarrhythmics are Quinidine and Dixopyramide?

How do they work?

A

Class Ia anti-arrhythmics.

Sodium channel blockers, increasing the refractory period.

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6
Q

What class of antiarrhythmics are Lignocaine and Phenytoin?

How do they work?

A

Class Ib anti-arrhythmics.

Sodium channel blockers, decreasing the refractory period

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7
Q

What class of antiarrhythmics are flecainide, encainide and propafanone?

How do they work?

A

Class Ic anti-arrhythmics.

Sodium channel blockers, depress phase 0. No affect on the refractory period.

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8
Q

What side effects can occur with Class Ia anti-arrhythmics?

A 
Anti-muscarinic side effects:
Blurry vision
Dry mouth
Constipation
Urinary retention
Anhidrosis
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9
Q

What side effects can occur with Class Ib anti-arrhythmics

A

Paraesthesias

Skin reactions: dry, scaly skin; eczema,

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10
Q

What side effects can occur with Class Ic anti-arrhythmics?

A

Non-cardiac side effects are minimal.
However:
Myocardial suppression
Can be pro-arrhythmic

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11
Q

What are some examples of Class II anti-arrhythmics? How do they work? Is there any further classification?

A

Propanolol, labetolol: non-selective beta antagonist
Atenolol, bisoprolol cardioselective beta antagonist
Pindolol: partial beta agonist

Beta blockade slows the heart and prevents re-entrant tachycardia.

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12
Q

How does pindolol work?

A 
It is a class II anti-arrhythmic and a partial beta agonist. It binds to beta adrenoceptors and causes partial activation. 
This partial activation is less than intrinsic noradrenaline, so there is still an effective beta-blockade.
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13
Q

When are Class I anti-arrhythmics most useful? Why?

A

During tachycardias: they work by binding to open sodium channels, which are more available during fast heart rhythms.

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14
Q

What side effects can occur with Class II anti-arrhythmics?

A 
Bronchospasm in asthmatics
Precipitation of heart failure
Cold hands and feet
Central side effects: bad dreams
Fatigue
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15
Q

What class of anti-arrhythmic are Propranolol, Labetalol and Pindolol?

A

Class II:
Propranolol: non-selective beta antagonist
Labetalol: cardioselective beta antagonist
Pindolol: partial beta agonist.

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16
Q

What are some examples of Class III anti-arrhythmics?

A

Amiodarone

Sotolol

17
Q

What side effects can occur with amiodarone?

A

Grey skin discolouration
Lung fibrosis
Hypothyroidism (Amiodarone’s structure contains iodine)

18
Q

What are some examples of class IV anti-arrhythmics?

A

Amlodipine

Verapamil

19
Q

What are some examples of antiarrhythmics that aren’t Class I-IV?

A

Adenosine

Digoxin

20
Q

How does Digoxin work?

A

It competitively binds to the Na-K ATPase on the outside of cardiac myocytes. This increases the calcium content inside of the cell, slightly increasing contractility.
It also reduces conduction within the AV node.

21
Q

What side effects might occur with Digoxin?

A

Supraventricular tacchyarrhythmias
Nausea - severity depends on blood digoxin levels
Xanthopsia - yellow tinge to vision.

22
Q

What class of drug is Digoxin?

A

Cardiac glycoside (Anti-arrhythmic)

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