Drug Interactions 2- sodium and potassium channels

Question 0

Benzocaine

Answer 0

Local Anaesthetic

Uncharged sodium channel blocker
No pH dependence but works via both hydrophilic and hydrophobic pathways.
Hydrophilic pathway (use dependent) - blocks channel via cytoplasm
Hydrophobic - blocks channel via membrane

Question 1

Lidocaine

Answer 1

Local anaesthetic:

Stabilises sodium channels in inactivated state => hyperpolarisation
Charge dependent
Blocks best when in charged state (at high pH)
Use dependent - ‘fast in, fast out’
Blocks inactivated channels
Initial block increased by giving a hyperpolarising pre-pulse

Question 2

Quinidine

Answer 2

Local Anaesthetic

Na channel blocker
Use dependence at low rates of stimulation - ‘slow in, slow out’
Class IA antidysrhythmic

Question 3

Tetrodotoxin

Answer 3

Sodium channel blocker
Blocks externally- no use dependence
Contains guanidium group

Question 4

Nicorandil

Answer 4

Potassium channel opener (Katp channel)
Vasodilator
Used in treatment of angina
Also activates guanylyl cyclase

Question 5

Minoxidil

Answer 5

Potassium channel opener
Vasodilator
Promotes hair growth (used in male alopecia)

Question 6

Glibenclamide

Answer 6

Sulphonylurea receptor -> Closes Katp channel -> depol -> VG Ca2+ -> insulin release

Effective in type II diabetes