(10.1) Anti-Arrhythmic Drugs

Question 1

How does class II drugs work? Give examples to the subtypes (receptor selectivity).

Answer 1

• Beta blockers -> -Ve introphy and chrontrophy
• Non selective: Propanolol
• Beta 1 selective: Atenolol, Bisoprolol

Question 2

How does class I drug act? Give two examples.

Answer 2

• Sodium channel blocker - block to ACTIVE channels (especially in damaged area) -> slows phase 0 depolarisation, NOT AP duration
• Flecainide (class 1a)
• lidocaine (class 1b)

Question 3

Class I drugs are further subclassified, how?

Answer 3

• 1a: intermediate association/dissociation
• 1b: fast association/dissociation eg. Lidocaine
• 1c: slow association/dissociation eg. Flecainide

Question 4

What conditions does beta antagonists used but with caution?

Answer 4

• COPD

- Heart failure

Question 5

What conditions are contra-indicated with beta antagonist?

Answer 5

• Asthma

- AVN block

Question 6

How does class III work? Name an example.

Answer 6

• Potassium channel blocker -> prolong repolarisation -> prolong refractory period -> prevent re-entry
• Amiodarone

Question 7

Amiodarone is not used preferably, due to variety of ADRs, and interactions in body, suggest some.

Answer 7

• Large Vd-> need large loading dose
• Long T1/2
• Hepatitis
• Hyper/Hypo thyroidism
• Peripheral neuropathy

Question 8

How do class IV drugs work? Name an example

Answer 8

• Ca channel blockers -> prolong phase 4 refractory period of AVN -> slow heart rate
• Verapamil, Diltiazem

Question 9

Suggest 3 indications of calcium channel blocker.

Answer 9

• Angina
• Hypertension
• Atrial fibrillation as rate control

Question 10

How does adenosine work? Suggest uses of it

Answer 10

• Act on alpha 1 adrenoreceptor on AVN -> open K channels -> hyperpolarisation -> temporary heart blocking
• Treat SVT if re entry via AVN (eg won’t work if other entry loops)

Question 11

How does Digoxin work?

Answer 11

• Increase vagal outflow -> -ve chronotrophy

Question 12

Describe the treatment of AF with reference to both rhythm and rate control.

Answer 12

• Rate control: Beta blocker/CCB (first choice), Digoxin (2nd choice)
• Rhythm control: Flecainide (1st choice), Amiodarone (2nd choice)

Question 13

What drugs can be used to treat SVT?

Answer 13

• Adenosine

- Amiodarone (class III)

Question 14

What do you use to treat Paroxysmal AF?

Answer 14

Flecainide (class I)