Prilocaine
Chemical
Amide local anaesthetic
Use
Regional anaesthesia
Commonly only used for IV regional anaesthesia (Bier’s block)
EMLA
Presentation
Clear colourless solution
Ointment
Dose
Toxic dose is 6mg/kg
(8mg/kg with felypressin)
Potency similar to lignocaine but longer duration of action (x1.5)
Route
Topically, infiltration, epidural
Onset
Slow
MoA
Blocks Na channels of neurons, blocking them in the inactive state
Reduces neuronal depolarisation through blocking action potentials
PD
CVS
- Less cardiotoxic, often used for IV regional anaesthesia
- Decreases: rate of Ph IV depolarisation, duration of AP, effective refractory period, conduction velocity
- Slight increase SVR (low doses)
- High doses: reduces SVR, -ve inotropy, Cardiovascular Collapse
RESP
- Bronchodilation
- Respiratory depression (toxic dose)
CNS
- Excitation: light headedness, diszziness, tinnitus, seizures
- Depression: drowsiness, disorientation, coma
GI
- Reduces bowel contractility
PK
A
IC>epidural>brachial plx > subcut
Dose (liner reln)
Vasconstrictors – delay absportion
D
Large Vd
55% PPB (a1 glycoprotein)
M
Most rapid of all amides
Metabolism in liver, kidney & lung
Metabolised to ortho-toluidine
Ortho-toludine is an oxidising compound
Can oxidise Hb to MetHb
E
t1/2β 108mins
Adverse Effects
>600mg Prilocaine doses are sufficient to cause MetHb
To produce cyanosis 10% of Hb must be converted to MetHB
Successfully Tx w methylene blue 1-2mg/kg IV
Increases hepatic transaminases