local anaesthetics

Question 1

Amide-containing local anaesthetics

Answer 1

• Articaine – short-acting, rapid onset
• Lidocaine (lignocaine) – medium-acting, rapid onset
• Prilocaine – medium-acting, no vasodilation
• Bupivacaine \ Levobupivacaine – long-acting, slow onset

Question 2

ester containing local anaesthetics

Answer 2

• Tetracaine – long-acting, very slow onset
• Chloroprocaine – medium-acting
• Benzocaine – atypical mechanism of action

Question 3

why is there side effects

Answer 3

Nonspecific to nerves, hence side-effects.

entry into systematic circulation

Question 4

what are the side effects

Answer 4

CVS:
-dysrhythmias
-sudden fall in blood pressure
CNS:
- Restlessness 
- tremors
- convulsions 
- respiratory centre
- depression 
- death

Question 5

routes of administration

Answer 5

surface 
infiltration
nerve block 
intravenous regional 
epidural (particularly bupivacaine) 
subarachnoid

Question 6

What EMLA is used for dental anaesthesia

Answer 6

mixture of lignocaine and prilocaine
MPT lower in mixture
Higher conc can be used
more chance to get across skin

Question 7

sensitivity to LA

Answer 7

diameter of the fibre 
myelination status 
length of nerve 
length of time exposed to drug 
concentration of drug

Question 8

LA

Answer 8

can exist as neutral or protonated
pH dependant
block when ionised vita intracellular binding site
but can’t pass through membrane when ionised
WEAK BASES
pKa 8-9

Question 9

Onset of action:

- describe use dependance

Answer 9

bind to open or inactivate channels

related to frequency of neuronal firing, faster onset in faster firing neurons

Question 10

Duration of action:

- dictated by rate of removal

Answer 10

• blood flow
• action of plasma esterases (ester linked LA only)
• hydrophobicity of drug

Question 11

Increasing duration

Answer 11

most LA cause vasodilation except cacaine and prilocaine