Heart & Diabetes Pharmacology III: Drugs and the Heart II

Question 1

What are the FOUR classes of Vaughan Williams drugs?

Answer 1

1. Class I - Na+ channel blockers
2. Class II - β-blockers (target SA node)
3. Class III - K+ channel blockers
4. Class IV - Ca2+ channel blockers

Question 2

What are the effects of Class I drugs on action potentials?

Answer 2

Non-nodal
* slows Phase 0 depolarisation
* some alter APD & ERP
* slow conduction velocity

Question 3

What are the effects of Class II drugs on action potentials?

Answer 3

Decrease sinus rate (SA) and conduction through the AV node

Question 4

What are the effects of Class III drugs on action potentials?

Answer 4

Prolong Phase 3 dépolarisation (ERP & APD)
* slow conduction velocity

Question 5

What are the effects of Class IV drugs on action potentials?

Answer 5

• Main effects on SA & AV nodes
• Slow Phase 0 depolarisation
• Decrease sinus rate (SA) and conduction velocity