LA types Lecture 4

Question 1

Lignocaine

Metabolism?

Answer 1

Metabolism: Liver via microsomal fixed function oxidases. Converted to monethylglycerine and xylidine.
Excreted via kidney; 10% unchanged, 80% active metabolites

Question 2

Lignocaine

Anaesthesia time?

Answer 2

Without vasodilator: pulpal 5-10 min and soft tissue 1-2 hrs

With 1:80000 adrenaline: pulpal anaesthesia 1-1.5hrs, soft tissue anaesthesia 3-5 hrs

Question 3

Max safe dose?

Answer 3

Plain solution- 3mg/kg up to 300mg

With 1:80000 adrenaline 7mg/kg up to 500mg

Question 4

Mepivacaine

Metabolism?

Answer 4

Metabolised by hepatic microsomal fixed function oxidases by hydroxylation and n-dymethylation reactions

Question 5

Mepivacaine advantages?

Answer 5

Little vasodilation so can be used as a plain solution
Low Pka so high Ph meaning more avaible in diffusable form and therefore better in sites of infection (acidic environment)

Question 6

Mepivacaine

Anaesthesia time

Answer 6

Plain solution: pulpal anaesthesia 20 min (infiltration), 40min (block). Sot tissue 2-3hours
With vasoconstrictor: pulpal 1-1.5 hrs. Soft tissue 3-5 hours

Question 7

Mepivacaine

Max safe dose?

Answer 7

4.4mg/Kg up to 600mg

Question 8

Prilocaine

Metabolism?

Answer 8

Toulidine derivative. Metabolised in the liver (to ortho-toulidine and N-propylalanine) but significant prportion is metabolsied in the lung and kidneys

Question 9

Prilocaine

Advantages?

Answer 9

Little vasodilation- plain solution.

Least toxic LA available with minimal effects on the CNS and CVS

Question 10

Prilocaine

Disadvantages?

Answer 10

4% plain- nerve paraethesia reported
Methomoglobenemia
3% solution with 0.03IU?mL felypressin- cause uterine contractions and prilocaine crosses the placenta the most of all LA’s

Question 11

Prilocaines

Max safe dose?

Answer 11

Plain solution- 6mg/Kg

With felypressin- 9mg/Kg up to 400mg

Question 12

Articaine

Metabolism?

Answer 12

90-95% in plasma and 10% in liver. Metabolite articanic acid is an inactive metabolite

Question 13

Articaine

Advantages?

Answer 13

Thiophene ring increases lipid solubility, giving better diffusion properties particularly in bone
Articanic acid is an inactive metabolite, then repeated injections over extended period may be safe to perform despite max dose, but max dose shouldn’t be exceeded in one injection period
Good anaesthsia in infected areas

Question 14

Articaine

Concerns?

Answer 14

Reports of nerve parasethsia in literature with the 4 % solution

Question 15

Articaine

Anaesthesia time?

Answer 15

With vasoconstrictor
Pulpal 1 hour, soft tissue 2-4hrs
NB: slighter faster action of onset than lignocaine

Question 16

Articaine good for use when?

Answer 16

Blocks contraindicated
Infected areas
Mandibular molars in the case of failed blocks
Multiple procedures requiring a number of injections

Question 17

Articaine max safe dose?

Answer 17

7mg/Kg up to 500mg

Question 18

Bupivicaine

Metabolism?

Answer 18

Metabolised in liver by amidases and excreted by kidney
Long half life of 2.7hrs with active metabollites
NB:most potent and toxic of all amide LA

Question 19

Bupivicaine

pKa?

Answer 19

High so slow onset of action, bu due to high protein binding once it works it results in profound anaesthesia

Question 20

Bupivicaine

Anaesthesia time and reasons?

Answer 20

Highly lipid soluble and binds powerfully to the protein receptor sites in sodium channels.
Pulpal anaesthesia-1.5-3hrs
Soft tissue anaesthesia 4-9 hrs

Question 21

Bupivicaine

Solution?

Answer 21

0.5% with 1:200,000 adrenaline

Question 22

Bupivicaine good for use when?

Answer 22

Cases requiring long anaesthesia

post operative

Question 23

Bupivicaine

Max safe dose?

Answer 23

1.5mg/Kg when used with adrenaline

Question 24

Reversal agent

Answer 24

Phentolamine Mesylate (OraVerse)- alpha adernergic receptor antagonist, reverses the effect of vasoconstrictors

Question 25

Reversal agent

Availability and dosage?

Answer 25

Not available in AUS
Administered on 1:1 basis
Rush of LA to liver and risk of toxicity increases

Question 26

Reversal agent

Contraindicated?

Answer 26

Younger than 6
Less than 15kg
Sensitive to Phentolamine Mesylate
MI
Angina
Coronary artery disease

Question 27

Lignocaine

Solution?

Answer 27

2% with 1:80000 adrenaline

Question 28

Mepivicaine

Solution?

Answer 28

3% plain or

2% with 1:100000 adrenaline

Question 29

Prilocaine

Solution?

Answer 29

4% plain or
#% with 0.03IU/mL felypressin

Question 30

Articaine

Solution?

Answer 30

4% with 1:100000 adrenaline