LA types Lecture 4 Flashcards
Lignocaine
Metabolism?
Metabolism: Liver via microsomal fixed function oxidases. Converted to monethylglycerine and xylidine.
Excreted via kidney; 10% unchanged, 80% active metabolites
Lignocaine
Anaesthesia time?
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
Max safe dose?
Plain solution- 3mg/kg up to 300mg
With 1:80000 adrenaline 7mg/kg up to 500mg
Mepivacaine
Metabolism?
Metabolised by hepatic microsomal fixed function oxidases by hydroxylation and n-dymethylation reactions
Mepivacaine advantages?
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)
Mepivacaine
Anaesthesia time
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
Mepivacaine
Max safe dose?
4.4mg/Kg up to 600mg
Prilocaine
Metabolism?
Toulidine derivative. Metabolised in the liver (to ortho-toulidine and N-propylalanine) but significant prportion is metabolsied in the lung and kidneys
Prilocaine
Advantages?
Little vasodilation- plain solution.
Least toxic LA available with minimal effects on the CNS and CVS
Prilocaine
Disadvantages?
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
Prilocaines
Max safe dose?
Plain solution- 6mg/Kg
With felypressin- 9mg/Kg up to 400mg
Articaine
Metabolism?
90-95% in plasma and 10% in liver. Metabolite articanic acid is an inactive metabolite
Articaine
Advantages?
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
Articaine
Concerns?
Reports of nerve parasethsia in literature with the 4 % solution
Articaine
Anaesthesia time?
With vasoconstrictor
Pulpal 1 hour, soft tissue 2-4hrs
NB: slighter faster action of onset than lignocaine
Articaine good for use when?
Blocks contraindicated
Infected areas
Mandibular molars in the case of failed blocks
Multiple procedures requiring a number of injections
Articaine max safe dose?
7mg/Kg up to 500mg
Bupivicaine
Metabolism?
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
Bupivicaine
pKa?
High so slow onset of action, bu due to high protein binding once it works it results in profound anaesthesia
Bupivicaine
Anaesthesia time and reasons?
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
Bupivicaine
Solution?
0.5% with 1:200,000 adrenaline
Bupivicaine good for use when?
Cases requiring long anaesthesia
post operative
Bupivicaine
Max safe dose?
1.5mg/Kg when used with adrenaline
Reversal agent
Phentolamine Mesylate (OraVerse)- alpha adernergic receptor antagonist, reverses the effect of vasoconstrictors
Reversal agent
Availability and dosage?
Not available in AUS
Administered on 1:1 basis
Rush of LA to liver and risk of toxicity increases
Reversal agent
Contraindicated?
Younger than 6 Less than 15kg Sensitive to Phentolamine Mesylate MI Angina Coronary artery disease
Lignocaine
Solution?
2% with 1:80000 adrenaline
Mepivicaine
Solution?
3% plain or
2% with 1:100000 adrenaline
Prilocaine
Solution?
4% plain or #% with 0.03IU/mL felypressin
Articaine
Solution?
4% with 1:100000 adrenaline
