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